MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 463 



The sections of these embryos were very kindly examined by Professors Joseph Leidy and W. 

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



The para.nite is certainly of great- interest. I caniml lincl any tlescrjpt ion of it in botanical literatim', although 

 it appears to lie a fungus belon^ini;- io Ch> triuiao-:r. 



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

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

 that the peripheral 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 with the parasitic growths and showed traces of degeneration. 



The parasitic bodies arc mainly (1) large naked cysts or encysted cells, and (2) very small 

 spore-like bodies. The naked cyst (c. s., Fig. I'M) is a thick shell which has collapsed and curled 

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

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

 light in a characteristic way. 



Other encysted cells contain a protoplasmic reticulutn (cs 1 ), and there are very similar but 

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

 bodies just described possibly represent zoosporaugia, and give rise to the myriads of minute 

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

 black dots) are minute, oval, and highly refractive. 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.s 2 ), which is due mostly, if not wholly, to refraction. 



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

 Besting 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 zoosporangia. These give rise to swarm 

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

 aquatic plants, Fungi, Alga?, and Phanerogams. 



According to De Bary resting spores are known to occur in certain species. These develop 

 directly into sporangia or produce them after a short intermediate stage, and appear to resemble 

 the sporangia in 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 

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

 1892. The part relating to the embryology 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 Alpheus minus of Say 

 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, May, 1892. 



