EPHIPPIAL OVA. 419 



the severity of the winter's cold. There seems a strong probability, 

 from the observations of Mr. Lubbock, that the ephippial eggs are true 

 sexual products, since males are to be found at the time when the 

 ephippia are developed, whilst it is certain that the ordinary eggs can 

 be produced non-sexually, and that the young that spring from them 

 can reproduce their race in like manner. It has been ascertained by 

 Dr. Baird that the young produced from the ephippial eggs have the 

 same power of continuing the race by non-sexual reproduction as the 

 young developed under ordinary circumstances. In most Entomostraca, 

 the young, when first hatched, have only the thoracic portion of the 

 body as yet developed, and possess but a small number of locomotive 

 organs. The eyes, too, are at first frequently wanting. The process of 

 development goes on with great rapidity, the animal at each successive 

 moult (which process takes place at intervals of a day or two) present- 

 ing some new parts and becoming more and more like its parent, the 

 females laying eggs before they have acquired their full size. 



(1075.) The cast shell carries with it the sheaths not only of the 

 limbs and plumes, but of the most delicate hairs and setae connected 

 with them. If the animal have previously sustained the loss of a 

 member, it is gradually renewed at the next moult, as in the higher 

 Crustacea. 



(1076.) Some authors have supposed, from the circumstance of all the 

 individuals which have been met with belonging to certain genera being 

 females, that some of these little beings were hermaphrodite, or self- 

 impregnating ; but such an opinion rests on very doubtful grounds, 

 especially as there seems good reason to believe that in many instances 

 the forms of the male and female of the same species are so different 

 that they might easily be mistaken for totally distinct animals. 



(1077.) The last point which we have to notice, in connexion with the 

 history of the Crustacea, is the progress of their development from the 

 embryo condition to the mature state. This is a subject which has 

 given rise to considerable discussion, especially as relates to the changes 

 which occur during the growth of the more highly organized forms, < 

 some authors contending that they leave the egg complete in all their 

 parts and presenting their adult configuration, while others assert that 

 they undergo changes so important as only to be comparable with the 

 metamorphoses of insects. 



(1078.) Among the Entomostraca such changes have been again and 

 again witnessed, and the appearances observed during their growth care- 

 fully recorded. From these observations very important results have 

 been obtained, inasmuch as many forms previously described as distinct 

 species have been found to be merely the same animal in different stages 

 of development. In Cyclops, for example, the newly-hatched embryo 

 possesses only four legs, and its body is round, having as yet no appear- 

 ance of caudal appendages : of young animals in this condition Miiller 



2E2 



