placed in the closet only a portion of its head and feet were covered, while at the time of being removed, a dense mat of radiating, branched filaments enveloped the whole animal. All the forms which I have met have either developed from decaying animal or vegetable matter, or caused its decay by their growth; and filaments separated entirely from all matrix, and placed under cover-glass, the whole covered by a bell-jar to keep it moist, showed, after some growth, that the protoplasm did not half fill the filaments. Hence, after this brief view, I have come to the conclusion that, according to the distinctions of the two groups given by our authorities, this family of truly parasitic plants must belong to the Physomycetes among the Fungi, where it is placed by Sachs (7,242) and Cornu. (2,5).

M. Cornu (2) separates the entire family into two main divisions-the Saprolegnieæ proper, and the Monoblepharida-the chief distinction lying in the zoospores, which, in the first group, are uniform with two unequal cilia, one attached at either end, or oval with two equal cilia attached in front; while in the second group they are ovate, and provided with a simple cilium. Moreover, it has been noted that in all the species of the Saprolegnieæ proper the wall of the filaments is formed of cellulose, giving a bluish reaction on the application of Shultze's solution, whereas in the Monoblepharidæ no reaction is given, showing that the walls are not formed of cellulose. Under the first division are included six genera, among which I have paid special attention to but two; Saprolegna and Achlya, and of which I shall treat further on. The second division contains but a single genus, Monoblepharis, and under that but three species have been described, while one of the forms which I shall consider further on doubtless adds a fourth.

To the Saprolegnieæ are attributed two modes of reproduction, which give the group particular interest. In one case, zoospores are produced which germinate and grow without the intervention of any male product; while in the other both male and female organs are present, and fertilization takes place giving rise to a spore, which remains at rest a much longer time before germinating than in the former case. The first of these methods I have carefully studied, and a full description follows under the genus Saprolegnia; while the second form has been particularly noted in the genus Achlya.

SAPROLEGNIA.

I can give no specific designation to the plant which I have included under this genus, for, as far as studied, there were presented characters different from descriptions to which I have had access; and yet I can not justly place it under a distinct species, since I have not been able to study the several modes of reproduction, in which rest very important characters. It is a form which seriously attacked Menobranchus kept at different times in a tank at the University. They seemed to produce considerable irritation, and death was sure to take place in a few days. In the cases noted, the plants first appeared just anterior to the brain, then posterior to each set of gills, and, finally establishing itself on portions of the body and legs soon completely covered the whole animal.

This is quite different from the way in which I have since noticed other forms to attack fishes, for with them growth took place equally on a large portion of the animal, the filaments being of the same age and covering the whole body. I have already noticed the effect of this plant upon the animal, i. e., that long before death, the parts infested had the appearance of decomposing flesh, and could be easily torn from the animal before the filaments would break; the parts thus exposed had the appearance of being inflamed.

The fungus appears in dense, grayish mats of filaments, averaging about 6 mm. in length, and when closely observed the Sporangia are just noticable from their darker appearance. (Pl. VI., Fig. 1.) Carefully removing a cluster of filaments by means of a pair of forceps, and placing it under a cover-glass, a great difference is noted in different filaments according to age. When young the tip is always clear, while just below it becomes very dark from its granular contents, these granules becoming less dense so that the main part of the filament is nearly clear.

As they reach their growth the granules concentrate more at the apex, and, after becoming so dense as to render that portion of the filament opaque, a septum is formed producing a terminal cell with a length some eight times its breadth.

This sporangium is always larger than the filament; is sometimes cylindrical, but generally club-shaped. In four hours after the septum is formed, the granules have so rearranged themselves as to produce a mottled appearance shown

in Fig. 4, Pl. IV., and in four hours more the contents of the sporangium are arranged into many spherical bodies (Fig. 5) of about one-fourth the diameter of the sac, and in some cases that I timed they passed from the sporangium is about twenty-four hours after the septum was formed.

Just before escaping the zoospores at the base always take on an oscillating motion, which passes to the zoospores next above and so on to the summit, causing such a pressure that in less than a minute the power is such as to cause a rupturing of the sporangium, which, in normal conditions, always takes place at the summit. The zoospores now pass out, at first very rapidly, so that it is impossible to count them, but when about one-half out they become more quiet, seldom losing their motion however, until all have passed from the sac. In passing out they are very much constricted, so that if any lose their power of motion before they have escaped, it is impossible for them to pass out. Having passed from the sporangium, which was emptied in one minute, they swarmed around very lively for nearly four minutes, at the end of which time they settled down, lost their cilia and became spherical. (Fig. 9.) At the end of one hour and thirty minutes they had germinated (Fig. 10.) and one hour later growth had proceeded to the extent shown in Fig. 7. Except at the tip, the growing filament was perfectly clear. In another case zoospores given off at 12.30 o'clock were found germinated at 3.30, at which time they underwent a very singular change. A swelling appeared on the zoospore similar to that seen in germination, but, instead of elongating, it gradually enlarged into a spherical body, at the same time the contents of another cell shrank proportionately from the opposite side, and in forty seconds there was nothing left of the old zoospore but a delicate transparent sac. This new body took on an oscillating motion and in two minutes separated itself from the old sac, taking on an irregular form,' after which it swam around for three minutes, then settled down and became spherical, the larger granules settling to one side. Germination took place twenty-five minutes later. The same change took place in all the zoospores noted from this sporangium, and the same was seen in other cases, but as a rule it does not occur. The sporangium was

I have since found this change spoken of by M. Cornu, who also says that this new body is provided with two cilia, but in these specimens I saw none.