88 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nature of these organisms, and established from them a new genus, 

 Olpidiopsis, of ChytridiacesB, and this view was subsequently adopted 

 by Pringsheim. 



A. Fischer has now subjected these bodies to a fresh careful 

 examination, and aj^pears to have fully established their parasitic 

 nature, by following their development and causing them to germinate 

 on filaments of Saprolegnia. 



The swarm-spores from the smooth sporangia vary greatly in size, 

 averaging between 4 and 8 /x, about twice as long as broad, and 

 biciliated, one cilium being attached to the anterior end, the other to 

 the middle of one side ; in the interior is a dark body, which is not 

 a nucleus, but rather a drop of oil. The zoospore is enclosed in a 

 delicate membrane of cellulo?e, which is thrown off when it penetrates 

 the host. With regard to that part of the Saprolegnia attacked by the 

 parasite, the author found that the zoospores of Olpidiopsis did not 

 attack those of their host while still in a motile condition, but only 

 after they had come to rest, and then without any passage of the con- 

 tents of one into the other. But to the young filaments of Saprolegnia 

 they attached themselves readily, pierced the filaments by means of a 

 small tube, and emptied their contents into it. The contents then 

 rounded themselves off within the filaments of the host to a motionless 

 body, which soon displayed amoeboid motions. These increase greatly 

 in size at the expense of the protoplasm of the Saprolegnia-^lament. 

 Ultimately the movement ceases, the body contracts into a denser 

 spherical mass, and soon becomes evidently clothed with a cellulose- 

 membrane, and the granules which have already been formed in it 

 increase in number. It has thus developed into a sporangium or 

 Stachelkugel, containing a number of refractive granules. The mem- 

 brane of this body, as well as the spines with which it is covered, are 

 composed of cellulose. The cellule adjacente, which Cornu always 

 found in connection with these bodies, does not appear to be invariably 

 present, and cannot have, as he supposed, any sexual function. The 

 spines are occasionally wanting. 



While still within the filaments of the host, the granules in the 

 sporangium gradually develop into zoospores. Before this takes place 

 it has put out one or more tubes which pierce the cell-wall of the 

 filament, attaining sometimes a very considerable length, and oc- 

 casionally branching. At length the zoospores escape through this 

 neck with great rapidity, and in very large numbers. They resemble 

 in every respect those produced in the spineless sporangia, except that 

 they are larger. The spiny sporangia sometimes remain for a con- 

 siderable time in a resting state, in which case vacuoles have pre- 

 viously been formed in them. 



In pure water the zoospores from the spiny sporangia either 

 perish or put out a small germinating filament. If Saprolegnia is 

 present in the water, they attach themselves to the filament, perforate 

 it by means of the tube, and empty their contents into it in the same 

 way as those from the smooth sporangia. The result is always the 

 production within the host of a smooth and not of a spiny sjwrangium. 

 Otherwise, the process of germination is the same ; but the smooth 



