312 Tlic Oogenesis of .the Tortoise 



Watase, and the writer (Wilson) that all the promorphological features 

 of the ovum are of secondary origin; that the egg-cytoplasm is at the 

 beginning isotropous, i. e., indifferent or homaxial, and gradually ac- 

 quires its promorphological features during its preembryonic history/ 



In the work of the writers cited above, the literature on the subject up 

 to the present time is extensively reviewed, especially by Wilson, 84. I 

 may perhaps be justified, therefore, in confining myself in the present 

 paper to a concise statement of my own observations. To show their 

 relation to the work of other observers, and the bearing of my conclu- 

 sions on present-day theories, would make my paper undesirably lengthy 

 and involved. I hope in the near future to consider this phase of the 

 subject in connection with observations that I have made on the ovarian 

 Qgg of the crayfish. 



My present observations have been made on the ovarian egg of the 

 Tortoise — Clemmys marmoraia. I have found it a favorable egg to 

 work with, and have been gratified to find so many of my conclusions 

 regarding tlic history and organization of tlie egg of Limulus, beautifully 

 confirmed. 



Regarding ]ny paper on that subject, I take pleasure in expressing here 

 my appreciation of the favorable mention which it has received; and I 

 desire especially to express my thanks to Prof. C. F. Hodge of Chirk 

 University, to Prof. Dr. P. Pick of Lcipsic, and to Dr. Fritjof Nansen 

 of Christiania for very kind courtesies and favors. 



DESCRIPTION OF THE TORTOISE. 



Clemmys marmoraia is a tortoise inhabiting the western part of North 

 America. I liave had no opportunity to study its distribution. But as 

 I am not aware that it exists east of the Rocky Mountains, and as it is 

 not mentioned in Jordan's Manual of the Vertebrates, I assume that it is 

 not common. It inhabits tlie ditches, pools and ponds tributary to the 

 Yakima River in central Washington. My identification is based on 

 three specimens found in the Museum of Natural History at Victoria, 

 British Columbia. The following description may not be out of place 

 here : 



Carapace ovate, in the adult consideral)ly elongate; margin flaring, 

 not strongly convex; highest in the middle; length from head to end of 

 tail, ten inches; plastron of twelve plates covering the whole under- 

 surface; lobes not hinged; alveolar surface of jaws medium in width; 

 alveolar groove visible; upper jaw slightly notched in front; carapace 



' The Cell in Development and Inheritance. 



