242 ALICE THING 



This short resume proves that most authors agree upon the 

 existence of protoplasmic bridges connecting the epitheUal cells 

 with the egg cytoplasm. But when they mention the homogene- 

 ous cuticular substance few give satisfactory descriptions and 

 illustrations of the origin of this or of its structure in later phases 

 of development. Only Regaud and Dubreuil go into the subject 

 in detail; they lay emphasis upon the different stages of its 

 development from the exoplastic fibers formed between the epi- 

 thehal cells. The object of the present paper is to show that 

 this membrane in the species studied consists neither of real 

 cytoplasmic structures nor of real exoplastic structures but of 

 intercellular substance and of cytoplasmic prolongations of the 

 epithelial cells combined in a definite manner. The intercellular 

 substance is represented by a series of walls ramified and anasto- 

 mosed in such a way as to create cylinders or canals of which the 

 transverse section appears as a reticular network. Extending 

 down through these cylinders cytoplasmic filaments from the 

 epithelial cells make their w^ay to the yolk substance. 



MATERIAL AND :\IETHODS (INCLUDING POSSIBLE SOURCES 



OF ERROR) 



Twenty-one series have been prepared from the ovarian eggs 

 of the following turtles: Clemmys guttatus (Schneider), Grap- 

 temys geographicus (Lesueur), Emydoidea blandingi (Holbr.), 

 Aromochelys odoratus (Latr.) and Chrj'^semys picta (Hermann) 

 in various stages of growth. The identification of these species 

 is so simple that I shall not stay to discuss the particular features 

 by which they were identified. The animals were killed as soon 

 as possible after their arrival in the laboratory to reduce errors 

 in observation, the result of any prolonged starvation due to 

 improper feeding, a condition which has marked influence upon 

 the general ovarian structure as shown recently by Walsh (Loeb 

 '17). The time which elapsed between the capture of the turtles 

 and their arrival in the laboratory and the conditions under which 

 they were kept prior to their arrival are not known. The major- 

 ity of the ovaries examined had the appearance of being perfectly 



