D. J. SCOURFIELD OX EPHIPPIA OF LYNCEID ENTOJIOSTRACA. 227 



the line of junction between the head-shield and the valves, can 

 be made out in the positions indicated in the figure. The 

 posterior end of the former line turns off in the direction of the 

 ventral margin of the shell, not very far after reaching the 

 middle of the valve — seeming to indicate that a very considerable 

 portion of the original shell margins will be permanently 

 attached to the ephippium. It is possible that this is correlated 

 in some way with the stopping short of the dorsal thickening 

 already alluded to. The inner lining of the carapace can be 

 seen to be much increased and thrown into curious folds, showing 

 that provision is being made for the special protection of the 

 egg by investing membranes. 



Alona tenuicaudis Sars. 



In one respect the ephippium of this species is unique, so far 

 as my experience goes, for it consists of the whole shell of the 

 animal, with the exception, of course, of the head-shield (see 

 Fig. 13). There is no sign of any tendency for the ventral to 

 break away from the middle and dorsal parts of the valves. 

 The shell markings are also normal, but the back shows the 

 usual chitinous thickening seen in ephippia, and there is a certain 

 amount of darkening extending from the back well over the egg. 

 This ephippium also presents us with another illustration of the 

 remarkable development of the inner lining of the shell. It will 

 be seen from the drawing that the egg is embedded in a great 

 mass of irregular cellular tissue, almost exactly similar in 

 structure to that found in Alonopsis ambigua, already described. 

 This "packing" fills up a large portion of the shell, and even 

 projects from between the anterior margins. For the most part 

 it is very irregular, but at the back it appears to be composed 

 of rather long prismatic cells, the walls of which exhibit fine 

 striations, as shown in Fig. 14. I had the opportunity on one 

 occasion of isolating an ephippial female of this species in which 

 the winter egg was already extruded, "but otherwise showed no 

 sign of ephippial modification except a faint darkening of the 

 shell. The next day, however, the cellular structures within the 

 shell were quite evident, and could be plainly seen to be produced 

 by the inner layer of the skin. The cell-walls were still colour- 

 less (they are darkened and chitinous in the moulted ephippium), 

 while the interspaces were filled with granular matter. At the 



