22 EEVIEWS. 



IV. — Natuegeschichte dee Daphniden* (Natural History of the Daph- 

 nidae). By Prof. Franz. Leydig. Eeviewed by J. Lubbock, Esq. 



Feom the time of Leeuwenhoek to the present, no group of Crustacea has 

 excited more interest, or been more studied by naturalists, than the 

 genus Daphnia, or, perhaps, to speak more precisely, the Family Daph- 

 niidse. So far, however, from exhausting the subject, these investiga- 

 tions have, in the present case, as in all other matters of science, opened 

 out a still more interesting field for future labours, and suggested more 

 questions than they have answered. 



In the present memoir, Prof. Leydig gives a description of all the 

 known species, and an interesting essay on their anatomy and embry- 

 ology, the whole being illustrated by excellent figures. We are also 

 made acquainted, for the first time, with several new species, and espe- 

 cially with a very curious new form, called by Prof. Leydig, Bythotre- 

 phes longimanus, and found by him in the stomach of Coregonus Wart- 

 manni, of which, indeed, it appears in some localities to form the chief 

 nourishment. And yet, though it must be so abundant, Prof. Leydig 

 was unable to obtain a single specimen from the lake itself; but as the 

 Coregonus is generally found at considerable depths, he infers that per- 

 haps the Bythotrephes also seldom comes to the surface. The female only 

 has as yet been discovered. The animal has the large antenna?, and the 

 large eye as in Polyphemus, but the latter has longer lenses. The recep- 

 tacle for the eggs is almost spherical, and so distinctly separated from the 

 rest of the body, that it much resembles the abdomen of some spiders. 

 There are four pairs of legs : the first is very much elongated, double as 

 long as the rest, and five- jointed ; the other three are not unlike those of 

 Polyphemus. The abdomen also is very remarkable, and ends in a spine, 

 half as long again as the rest of the body ; and which, with the long 

 anterior legs, the large eye, and the spherical receptacle, gives the whole 

 animal a most peculiar appearance. 



Since I have [had the advantage of reading Professor Leydig' s 

 work, I have had no opportunity of again examining the animals, and 

 am therefore not now in a position to offer any new observations of my 

 own with reference to those points as to which we differ ; it seemed 

 to me, however, that it was right to put my name to this review, be- 

 cause it will be necessary for me to refer more than once to my paper 

 on Daphnia (Phil. Trans. 1857) ; and because, while fully admitting 

 the great value and interest of the present work, I shall still be com- 

 pelled to differ from Prof. Leydig on one or two important points. 



Prof. Leydig adheres to the opinion that the agamic eggs of Articu- 

 lata are internal buds, or as he would perhaps prefer to call them 

 ' 'germs" (Keime), and not to be confounded with true eggs ; although 

 he admits that in the Polyzoa and Rotatoria the so-called buds agree 



* 4to. Tubingen, 1860, pp. 252. 



