50 TWELFTH ANNUAL REPORT. 



subject by the writer, but it was unfortunately interrupted before 

 completion. The most promising method of persuing the investi- 

 gation is that of sectioning ephippial females in various stages 

 with the microtome. A preparation of soap was employed with 

 partial success as a medium for embedding, and figures of some of 

 the many sections made are drawn on plate P. Figure 10 is a ver- 

 tical section through the middle of an ephippium which has been 

 cast off. The outer and inner shell layers are distinct and one of 

 the eggs is divided in the middle. No pigment or protecting ma- 

 terial was deposited in this case, which is the simplest possible. 

 Fig. 9 represents a section just back of the head; it passes diagon- 

 ally, severing the heart longitudinally (h). The intestine (a), the 

 ovaries (g), the mandible (m), the labrum (1), and certain suspen- 

 sorial muscles (?) are seen in situ. Only a portion of the ephip- 

 pium is cut and the double layers enclose a large mass of protec- 

 tive matter. Fig. 8 is a vertical section through the middle of the 

 animal, and the usual form of the ephippium is seen with its large 

 amount of protective matter obscuring all else. Fig. 7 is a longi- 

 tudinal section of an ephippium similar to that seen in Fig. 10. It 

 is hoped to present at some more appropriate time a fuller account 

 of the formation and process of moulting this saddle. 



Development of Daphnia. 



Although the careful researches of Clans and Grobben have ad- 

 ded much to our otherwise rather meager knowledge of the develop- 

 ment of the cladocera, there still remain many interesting points, 

 particularly with reference to the individual species, which merit 

 careful study. 



The following observations relate to the single species (D. 

 schffifferi) which was available during a short stay in Leipzig: 



The winter eggs of D. schasflferi are t\\o in number and are 

 lodged in the well known manner in an ephippium. 



The shape of these eggs is sharply ovoid, there being no distin- 

 guishable difference between the two ends. The position in the 

 ephippium is not, as might be expected, with the longer diameter 

 paralled to the axis of the body, but the posterior end is slightly 

 elevated. This is undoubtedly due to frequent elevation of the 

 abdomen between the valves during the extrusion of the eggs. 



The color is dark green and the only protection as the egg leaves 

 the ovary is a thick, tough shell which is at firEt so soft as to be 

 susceptible to pressure. It is thus reticulated, apparently through 

 the simple pressure of the walls of the ephippium. 



