334 LOUIS M. HICKERNELL. 



of the results obtained to date. A more detailed account based 

 upon further work will appear in a future publication. 



The anatomy of the Philodinidse has been described by Janson 

 (1893). The most conspicuous organs in the living animal are 

 those of the reproductive and the alimentary systems. The 

 latter begins with the buccal cavity at the base of the trochal 

 organs. This narrows down to a short tube leading to the 

 mastax. The mastax, with the digestive glands surrounding 

 it, is followed by the thin-walled esophagus which leads into the 

 thick-walled stomach. The posterior end of the latter is con- 

 tinued by the "blasendarm" which leads to the cloaca and 

 thence to the anus. The reproductive organs consist of two more 

 or less spindle-shaped bodies lying on either side of the stomach. 

 These are the ovaries and the vitellaria and they may at all times 

 be recognized by their prominent nuclei. The nephridia with 

 their flame cells are easily observed in the living animal. In the 

 foot are found the glands which secrete a substance which enables 

 the animal to adhere to different objects. The head region con- 

 tains several large coronal cells with large nuclei. 



A cross section of a normal extended P. roseola through the 

 mid-body region is shown in Fig. I. The vitellaria have enor- 

 mous nuclei, consisting of a central karyosome surrounded by a 

 clear homogeneous area and peripherally by a distinct nuclear 

 membrane. This is the "nucleolar nucleus" of Carnoy and this 

 type of nucleus is characteristic of the greater part of the cells 

 of the animal. The cytoplasm of the vitellarium, which is 

 syncytial in nature, is made up of granules of varying sizes and 

 these granules appear in different patterns particularly when a 

 variety of fixatives are used; it has quite an affinity for nuclear 

 stains as is usual with yolk structures. The cytoplasm of the 

 ovary does not differ essentially from that of the vitellarium. 

 Ovary and vitellarium are each surrounded by a thin membrane. 

 Figs. I and 4 show characteristic sections through normal 

 reproductive glands. 



The cytological structure of the stomach of the Philodinidae 

 has been described by Zelinka ('86) in the case of Callidina 

 symbiotica, by Janson ('93), and more recently by de Beauchamp 

 ('09), in the case of Callidina socialis. The lumen, the position 



