the flea there was a somewhat kidney-shaped plate (drawn on the blackboard) containing certain wheel-shaped markings, with a hair starting from each. The question was whether any part bearing similar hairs should also be called a pygidium, or whether it should only be given to an homologous part.

Mr. Davis did not think that he was bound to prove the identity of the thing as being a pygidium; it was for others to do that. What he had endeavoured to do was to show that in all these insects there were similar organs, and that they served similar purposes.

Mr. Beck did not quite understand the question in dispute; it seemed to him to be whether the term was rightly applied to the object or not, or whether it only applied to that portion of the "shell" which in the flea had a certain structure upon it. They all knew that certain portions of an insect had certain names given to them, and Mr. Stewart stated that there was a certain portion of the flea called the pygidium which happened to have upon it the very beautiful object which was ordinarily called by the same name by microscopists. The question was, were they right in calling this beautiful portion the pygidium? If this was so, and it was a special organ, there might be a similar organ found in other insects. Mr. Davis had been endeavouring to trace a similar organ in others, and having found it there, he called it also a pygidium, whereas Mr. Stewart said the term applied to a position only. He thought the two things might very well be brought into harmony without much difficulty.

The President said that the term pygidium would really apply to the position of the part rather than to its special form or function. From its derivation the word would merely indicate something near the tail of the creature.

Mr. Stewart said he had no doubt as to what was the pygidium of the flea; what he had wanted to know was what Mr. Davis thought of the homology of the body which he had described.

The President said that there might be two things which were morphologically different, but which performed the same functions.

Mr. Crisp said that it would be remembered that they had recently had a paper by Mr. F. A. Bedwell, on the mastax of Melicerta ringens; since that paper appeared he had lent Mr. Bedwell the Zeiss oil-immersion (), and he read extracts from a letter from Mr. Bedwell after having used the glass :-"It is the most magical addition to the instrument, and I feel certain that it will revolutionize a vast mass of information; many papers will have to be rewritten, amongst others my last on the mastax of Melicerta ringens. Wherever organic texture is concerned, this glass makes the invisible visible. As an example, I send you two slides of mastax of M. ringens, and one of Rotifer vulgaris, by Lord Sydney G. Osborne. If you look at them with an ordinary, and then with the immersion, you will see that a part of the ramus in Melicerta which I have drawn in my picture as a plane surface, is exquisitely furrowed, and comes out like a revelation; while the teeth and notches in Rotifer vulgaris appear

at once, and you may work for an hour with an ordinary and never separate them. The slides will serve as well as anything to show the value of the glass."

He also read extracts from a letter received from Dr. Fripp, of Bristol, in regard to Mr. Dallinger's paper on the measurement of the diameter of the flagella of Bacterium termo. (The letter will be found on p. 337.)

Mr. Stewart exhibited and described with drawings on the blackboard a slide of Onchopora hirsuta which Mr. Weightman, of Liverpool, had sent to the Society.

Mr. Crisp exhibited (1) Zentmayer's "Centennial" microscope, which had obtained a medal at the Paris Exhibition. The stand is provided with three different stages; a mechanical one with the usual movements, a large circular one with concentric rotatory motion, and a small concentric rotating "diatom-stage" bevelled out on its under surface, so as to allow of extremely oblique illumination, or, if still greater obliquity is desired, the stage can be reversed and the slide attached beneath, so that the utmost freedom is obtained for oblique illumination. The sub-stage bar, carrying the mirror and condenser, is made to swing on a pinion adjusted so that the object itself forms the centre of rotation; thus the sub-stage appliances can be used at any degree of obliquity beneath the object, or they may be swung above the stage for illuminating opaque objects. (2) Photograph of the Tolles-Blackham microscope (lent by Mr. Mayall), showing the circular disk that had been devised to obtain a swinging motion to the sub-stage without infringing Mr. Zentmayer's patent. (3) Photograph by Col. Woodward of Amphipleura pellucida in balsam, by Tolles' immersion (glycerine) objective.

The following gentlemen were elected Fellows of the Society:Captain Peter G. Cunliffe; M. Julien Deby, Vice-President of the Belgian Society of Microscopy; Mr. John Morris, F.S.S., F.Z.S.

SCIENTIFIC EVENING.

The first Scientific Evening of the Session was held in the Libraries of King's College on the evening of Wednesday, the 27th November, 1878.

The following were the objects exhibited :

Mr. Beck:

Artificial siliceous deposit with markings resembling those on
Pleurosigma angulatum.

A new crystal-quinate of quinine-polarized.
Mr. Gorham's complementary colour disks.

Mr. C. Baker:

Double-stained vegetable tissues.

Zeiss's oil-immersion.

Micro-photograph, referred to at p. 300.

Mr. Thos. Bolton:

Ophrydium longipes, Cephalosiphon, Stephanosceros, and other Rotifers.

Raphidiophrys pallida—a Rhizopod new to this country.

Of this genus, Professor E. Ray Lankester writes:-" It was founded by Mr. Archer, of Dublin, who described a fine green specimen in the Q. J. Mic. Sc.,' 1869 (plate xvi.). It is characterized by having a single excentric nucleus, surrounded by dense protoplasm in which are three or four contractile vacuoles; outside this is a gelatinous investment, and in this are imbedded slightly curved siliceous spicules in masses. Delicate filamentous pseudopodia radiate through the gelatinous coat, and as in Actinosphærium send fibrous continuations to a central point in the protoplasm.

This species is colourless, Archer's species is green. I have seen all these points of structure to-day by treating the specimen on the slide of the microscope under cover-glass, first with osmic acid, then with picro-carmine, and then alternately with glycerine and water. The glycerine prevents the spicules being seen, being of the same refractive index, but renders the protoplasm clearer. The nucleus is only seen well after staining. The form is highly interesting, and one I was very glad to see."

Mr. Frank Crisp:

Zentmayer's double-stained and other preparations from the Paris Exhibition, with Zentmayer's "Centennial" stand and diatom stage.

Professor S. P. Thompson's Strobic Circles.

Mr. Thos. Curties:

Sections of stipes of ferns by M. Kruitcheruit, of New Orleans. Mr. W. G. Cocks:

A singular caterpillar found on the Eucalyptus in Adelaide. Mr. H. Crouch:

New-in. objective for dissecting microscope.

New microscope for students' use.

Spencer and Sons (New York) and dry and immersion objectives, 4-in. dry ditto, for which the gold medal was awarded at the late Paris Exhibition.

Mr. Bolton's new microscope revolving tables (2).

Mr. Enock:

Various tongues of Hymenoptera, prepared without pressure. Dr. Edmunds:

The four-faced immersion prism (with faces inclined at 60°, 49°, 41°, and 30°), referred to at p. 309.

VOL. I.

2 E

Mr. F. Fitch:

Balanus balanoides.

Chyle, stomach, and appendages of drone-fly.

Teeth of blow-fly shown in relief.

Mr. C. J. Fox:

Polariscope for convergent light, with mica and selenite com

binations.

Rev. T. W. Freckelton:

Macrospores and microspores from coal, compared with spores of
Selaginella selaginoides.

Mr. H. E. Freeman :

Eggs of Gasterophilus equi from body of female, showing provision for attachment to hairs of the horse.

Dr. W. J. Gray:

Rutilaria epsilon and other rare diatoms.

Messrs. J. How and Company:

Fossil wood with insect borings and excreta, &c.

A new microscope lamp.

Mr. J. Mayall, jun.:

Some special slides of Amphipleura pellucida.

Dr. Millar:

A new camera lucida, designed by Dr. Russell, of Lancaster.
Dr. Matthews:

Triceratium favus, arranged to show images of a black cross.
Stylaster sanguineus.

Mr. A. D. Michael:

The newly discovered male of Cheyletus venustissimus (see p. 313). Professor Owen, C.B.:

Sections of "Granicones," described at p. 233.

Mr. F. Oxley:

The so-called "Pygidia" of grasshoppers, crickets, &c.

Mr. Thos. Palmer:

Sections of butcher's broom, common cane, &c.

Mr. B. A. Priest:

Portion of the bag of a starfish from China.

Mr. W. W. Reeves:

Section through the cone (Lepidostrobus) of Lepidodendron, with spores in situ, from Lancashire coal-measures.

Mr. C. Stewart:

Section through the growing point of Anacharis alsinastrum.

Mr. A. Topping:

Various sections from the tail of a whale (stained).

Mr. F. H. Ward:

Sections (21) of various plants double stained by himself.

INDEX TO VOLUME I.