MBMOIUS OF THE NATIONAL ACADEMY OF SCIENCES. 463 



The sections of these embryos were very kindly examined by Professors .loseph Leldy and W. 

 G. Farlow. In reference to them Dr. Farlow writes as follows: 



The parasite is certainly of great interest. I eanuot tind any description of it iu botanical literature, although 

 it appears to be a I'linjjns beloni;iug to Chytridiacea-. 



The fungus has no mycelium, but is composed of single cells of various sizes. In a section 

 like that shown iu Fig. 199 nearly one hundred large cells or cysts can be counted, and it is seen 

 that the jieripbeial parts of the embryo are packed with them. These embryos were alive, 

 although the embryonic cells were considerably altered from their normal condition, where they 

 came in contact witli the parasitic growths and showed traces of degeneration. 



The parasitic bodies are mainly (1) large naked cysts or encysted cells, and (:-') very small 

 spore-like bodies. Tlie naked cyst {v. «., Fig. !!)!>) is a thick shell which has collapsed and curled 

 up with the escape of its contents. It is yellowish and is unafiected by staining reagents. The 

 surface of the cyst is covered with \ery uniform, short projections or tubercles, which refract the 

 light in a cliaracteristic way. 



Other encysted cells contain a protoplasmic reticulum (c*'), and there an^ very similar but 

 smaller bodies which are either naked or possess but a slight cuticuiar wall. These encysted 

 bodies Just described i)0ssiblj' represent zoosporaugia, and give rise to the myriads of minute 

 spores which occur in close relation with them. The spores (Fig. 199, ^7^, represented by small 

 black (lots) are minute, oval, and highly retractive. In the eye and other organs certain nuclei 

 take up the stain very eagerly and refuse to part with it. These are probably the nuclei of em- 

 bryonic cells which have undergone modification. Occasionally one of the cysts appears black 

 (c«^), which is due mostly, if not wholly, to refraction. 



According to Goebel, reproduction in the Chyfridiea' is effected by means of swarm spores. 

 Resting cells occur, which germinate and become sporangia, producing large numbers of swarm 

 spores. Some forms, like Chytridium, have no mycelium. Its single cells, which live on or within 

 the host plant, after reaching their full size become zoosporaugia. These give rise to swarm 

 spores, which are liberated into the water. The Chytridiece are described as parasites on other 

 aquatic plants. Fungi, Alga', and Phanerogams. 



According to Dc liary resting spores are known to occur iu certain species. These develop 

 directly into sporangia or i)roduce them after a short intermediate stage, and appear to resemble 

 the sporangia iu size and in possessing a warty cellulose coat. 



APPENDIX III. 



Some early abstracts of this work (Alpheus : A Study in the Development of Crustacea) were 

 included iu the Introduction published in the Johns Hopkins University Circulars, No. 97, April, 

 1S92. The part relating to the enibryology of Alpheus was here printed in its unrevised form, 

 and differs materially from the results of later studies which are given in this memoir. 



While this work was in press it was thought best to change the name Ali)heus minus of Saj- 

 to the correct form, Alpheus minor. As some of the pages were stereotyped before this correction 

 was made, both forms of the name appear. 



Adelbert College, 



Cleveland, Ohio. M;iy, 1892. 



