8 14 Genet al Notes-. [October, 



cially is this true in Crustacea, in so much that their condition 

 affords no sufficient evidence that the sexually mature animal is 

 in its historically perfect form. The enthusiasm elicited by the 

 discovery that certain amphibians, under some circumstances, 

 reproduce during a larval stage, was almost unparalleled, but I 

 believe it demonstrable that, not only species, but families of 

 lower Crustacea are normally sexually mature in a stage preced- 

 ing" actual maturity. 



VVe most naturally turn to the order Branchiopoda for a test, 

 since the most remarkable cases on record ot heterogeneous repro- 

 duction have recently been read in their history. We need only 

 mention the parthenogenetic summer brood of Daphnia,^ and the 

 case of heterogenesis discovered by G. O. Sars in Leptodora,^ in 

 which Sars concludes that L. Jiyalina has both *' dimorphous de- 

 velopment and alternation of generations." Nor are we disap- 

 pointed in looking among the Cladocera for examples of hetero- 

 genesis. During the winter semester of 1881-82, at Leipzig 

 University, we*had the opportunity of studying the development of 

 DapJinia magna [^scJiaffcri)^ and among other interesting facts 

 the following were elicited : 



The development proceeds in very much the way described for 

 Moina by Grobben.^ The secondary or swimming antennae have 

 an evident palpus in the nauplius stage, however, which makes 

 the parallel coniplete between Copepod and Branchipod Crusta- 

 cea. The heart and circulatory system apparently is formed dif- 

 ferently from the method given by Grobben. I may be permitted 

 to say in this connection, that the circulatory system is much 

 more complicated than hitherto described, and seems to originate 

 about a mass of deutoplasm which surrounds the intestinal canal 

 in the embryo, and which is a remainder of the food-yolk, 

 " Nd/i7^uiigsdottcr" of the egg. The embryo, in a comparatively 

 early age, begins to differentiate the walls of the valves, which 

 first appear as a fold over the maxillary region near the position 

 occupied by the heart, and extends gradually backwards in a 

 thick fold of turgid cells between which fluid flows. Quite 

 remarkable is it that from the dorsal region a process extends, 

 growing much more rapidly than the lateral portion till it 

 reaches the membrane of the Qgg, when it curves downward 

 and forwards till it reaches a position nearly half way from the 

 extremity of the abdomen to the maxillae. The method of 

 growth of this tail-like appendage of the shell is obscure, but 

 it seems to stand in close relation to the formation . of the brood- 



\ vSee J. Lubbock ; Phil. Trans., Vol. 147, p. 98. 



Cfr. R. Leuckarl : Archiv. f. Nature;., xxxi, and 



V. Siebold: Wahre Parthenogenesis bei Schmetterlingen und Bienen. 



^ G. O. Sars : Om en dimorph Udvikling samt Generations vexel hos Leptodora, 



^ Die. Entwicklungeschichte der Moina reciii'ostris, von Dr. Carl Grobben. Vienna, 

 1879- 



