D. J. SCOURFIELD ON THE EPHIPPIUM OF BOSMINA. 55 



and general opacity. Of course it is enclosed in a special covering 

 of its own, the egg-shell properly so called. In Fig. 3 a broken 

 egg-shell is shown, inside its protecting ephippium, after the 

 hatchino: out of the vouno; Bosmina. 



It will be apparent from the foregoing description that the 

 ephippium of Bosinina much more nearly approaches the homo- 

 logous structures found in the majority of the Lynceidae than it 

 does those of the Daphnidae. It is, in fact, scarcely worthy of the 

 name of an ephippium, as that word is commonly understood, but 

 would be more correctly designated as a proto-epbippium, a term 

 I have already employed for these less highly developed types 

 of protective egg-coverings. But this question is not of much 

 importance, and I have preferred to use the well-known word 

 '■• ephippium " throughout this paper. 



My observations on ephippia among the Bosminidae have been 

 confined to the two species already referred to and B. coryiuta, 

 which agrees exactly with B. longirostris. It is much to be 

 desired, therefore, that the investigations should be extended to 

 other species, especially to some of the more remarkable forms, 

 such as B. gihbera, B. herolinensis^ etc. Although I have no 

 doubt that all the species of the genus Bosmina will be found to 

 produce ephippia of the type already described, it- would be very 

 interesting to learn something of the extent of the variations 

 occurring in this respect in the genus. Still more interesting 

 would it be if we could discover what kind of ephippium is 

 formed by the peculiar Bosmiiiopsis deitersi recorded by J, 

 Richard from Argentina. 



Explanation of Plate 6. 



Fig. 1. Ephippium of Bosmina longirostris, side view x 150. 



„ 2. „ ,, ,, ., dorsal view x 140. 



,, 3. „ ,, „ ,, front view (somewhat 



flattened out of shape), x 140. 



„ 4. Bosmina longirostris, carrying ephippium and winter 

 e^g, xl30. 



„ 5. A portion of a lateral band of chitin, with adjacent 

 shell-markings (ephippium of B. longirostris), showing 

 how the areas enclosed by the latter are pitted, 

 whilst the band is structureless, x 350. 



