172 D. J. SCOURFIELD OX THE WINTER EGG OF A RARE WATER- FLEA. 



in the case of Chydorus splicericus, and gives a small drawing of it 

 on Plate XVI. (fig. 3 h). Schodler was the next, perhaps, to 

 observe resting eggs among the Lynceidse, for in 1846 he recorded 

 (9, p. 372) that he had observed in Eurycercus lamellatus that a 

 number of winter eggs were deposited at one time in the almost 

 unmodified cast shell of the mother, a fact which has since 

 been confirmed by Weismann (13). In a subsequent paper (10) 

 Schodler referred again to the same subject, and also briefly 

 alluded to the winter eggs of Chydorus sjihcericus and Peracantha 

 truncata. The earliest considerable contribution, however, to 

 our knowledge of the winter eggs of the Lynceida?, and their 

 comparatively simple protective coverings, which I have termed 

 elsewhere (11) " proto-ephippia," we owe to the patient observa- 

 tions of Kurz, who in 1874, in his paper " Dodekas neuer 

 Cladoceren " (3), recorded their existence in some sixteen 

 species belonging to the genera Cam2)tocercus, Alona, Pleiiroxus, 

 Chydorus, etc. Slightly later, 1877, Weismann independently 

 discovered the resting eggs of several species of the same 

 family,* some of which he briefly described and figured in the 

 second " Abhandlung " of his " Beitrage zur Naturgeschichte 

 der Daphnoiden " (13). Since that time, of course, the resting 

 eggs of many other species have been alluded to, in more 

 or less detail, by various writers. None of the proto-ephippia 

 which have been described, however, show any very close 

 approach to the true ephippia of the Daphnidse. The most 

 modified proto-ephippium hitherto recorded is probably that of 

 Chydorus sphcericus. But it will be readily admitted that, 

 although this structure exhibits many of the features of a genuine 

 ephippium in a more or less rudimentary condition [see Kurz 

 (3), p. 77, and Scourfield (11), p. 64], it is yet a long way behind 

 its highly evolved Daphnidan homologue. As, therefore, I have 

 recently found that the winter egg of Leydigia acanthocercoides 

 Fischer is provided with a proto-ephippium which exhibits a 

 considerable advance upon that of Chydorus sphcericus, and at the 

 same time possesses some other interesting features, I have thought 

 it worth while to bring forward my observations in a special 

 communication. 



* Both Kurz and Weismann seem to have thought that they were the first 

 to discover the winter eggs of Lynceidse, but as has been already mentioned 

 at least two previous authors had referred to these productions. 



