Mr. J. Lubbock on the Reproduction of Daphnia. 257 



By experiments that were made on the Hving worm, it is shown 

 that the pharyngeal chain of gangha are independent of the other 

 nervous centres, although subject to their influence, and are not 

 only competent of themselves to preside over the complicated move- 

 ments of the suctorial pharynx and mouth, but appear also to be 

 centres of reflex action. 



The present memoir concludes with some observations and re- 

 marks on the ganglionic cords of other Invertebrata. 



"An Account of the two Methods of Reproduction in Daphnia, 

 and of the Structure of the ' Ephippium.' " By John Lubbock, Esq., 

 F.G.S. 



In this paper the author describes the male organs and the structure 

 of the Ephippium in the genus Daphnia, and the double method of 

 reproduction by agamic and ephippial eggs. The author calls the 

 non-ephippial eggs agamic, but it is possible, though not probable, 

 that the ephippial eggs may be agamic also. In the male Daphnia 

 there are two small papillae above the posterior claws, but on the 

 ventral side of the anus, and on these being compressed, two streams 

 of minute rod-like bodies, with movements so gentle as to be scarcely 

 visible, will be seen to issue, one from each pajnlla. Nothing similar 

 has ever been observed in the female ; nor has any other sort of 

 spermatozoa ever been met with. These male organs have never 

 been described before. 



The author then proceeds to describe and figure the two sorts of 

 eggs in their earlier stages, which have not yet been mentioned by 

 any naturalist. The ephippial eggs differ from the agamic in their 

 determinate position and number. As a general rule, that is to say, 

 in seventeen cases out of twenty-three, the author has remarked that 

 ephippial eggs commence and are developed to a certain point. 



The development is as follows. One of the ovarian cells, always 

 at the posterior part of the ovary, swells a little, and becomes a ger- 

 minal vesicle ; round it are deposited a number of brownish granules, 

 while the other cells which may at first have existed in the same 

 ovarian mass cease to be visible. The deposition of dark granules, 

 in thirty- seven cases out of forty, after proceeding to a certain point, 

 ceased, and the embryo egg gradually disappeared. In the other 

 three cases it increased, and at length formed a dark mass on each 

 side of the intestinal canal. The author in two cases observed the 

 ephippial eggs pass from the ovary into the receptacle. 



The ephippium has been described by Strauss with considerable 

 accuracy, but he has been more or less misunderstood by all subse- 

 quent writers on the subject, and no one has explained the homo- 

 logies or connexions of the inner valve. The ephippium itself is 

 a locally altered portion of the carapace ; the outer valve of the 

 ephippium being a part of the outer layer of the epidermis, and 

 the inner valve the corresponding part of the inner layer. In cor- 

 sequence of this arrangement, the inner valve of the ephippium, 

 containing the ephippial eggs, is not attached by the hinge to the 

 outer valve, as has been generally stated, but actually lies at first in 



Ann. ^ Mag. N. Hist. Ser. :i. FoL xix. ' 17 



