Miscellaneous, 373 



Dimorphic Development and Alternation of Generations 

 in the Cladocera. 



Dr, G. 0. Sars has discovered a remarkable dimorphism and 

 alternation] of generations in Leptodora hijalina (" Om en dimorph 

 Udvikling samt Generationsvexel hos Leptodora," Forhandlinger 

 Vidensk.-Selsk. Christiania for 1873, p. 15, and plate). The de- 

 velopment from the ordinary summer-eggs, as already described by 

 E. P. Miiller, is without metamorphosis and like that of ordinary 

 Cladocera, the young when excluded from the egg agreeing essen- 

 tially with the adult ; while, according to Sars's observations, the 

 young are excluded from the winter-eggs in a very imperfect con- 

 dition, quite unlike the kno^vn young of any other Cladocera, and 

 pass through a marked postembryonal metamorphosis. In the 

 earliest observed stage of the young of this form, the body is obovate, 

 whoUy without segmentation, the compound eye wanting, while 

 there is a simple eye between the bases of the antennulaj, the 

 swimming-arms (antenna)) well developed, and the six paii-s of legs 

 represented only by minute processes projecting scarcely beyond the 

 sides of the body. But the most remarkable feature is the presence 

 of a pair of appendages tipped with cilia and nearly as long as the 

 body, which are evidently homologous with the mandibular palpi of 

 other Crustaceans, although these apjiendages have always been 

 supposed to be wanting in the species of Cladocera. Two subsequent 

 stages, gradually approaching the adult form, are described. The 

 adults from the winter-eggs have no vestige of the mandibular palpi 

 left ; yet the simple eye (which is wholly absent in ordinary indi- 

 viduals developed from summer-eggs) is persistent, and thus marks 

 a distinct generation. Three stages of the young from winter-eggs 

 are beautifully figured upon the plate accompanying the memoir. 



This remarkable species has, still more recently, been made the 

 subject of a very elaborate memoir by Prof. Weismann of Freiburg 

 ("Uebcr Eau und Lebenserscheinungen von Leptodora hyalina" Zeit- 

 schrift fiir wissensch. Zool. xxiv., Sept. 1874, pp. 349-418, plates 

 33-38), who, however, had not observed the peculiar development 

 of the winter-eggs. The occurrence of this genus in Lake Superior 

 is noticed in this Journal, vol. vii. p. 161, 1874. — Silliman's Ame- 

 rican Jovrnal, March 1875. 



On the Actinia? of the. Oceanic Coasts of France. 

 By M. P. Fischer. 



The Actiniae of the oceanic coasts of France (comprising in that 

 geographical region the Anglo-Xorman isles) number thirty-one 

 species : — Cerianthns membranaceus, Gmelin ; Edwardsia Harassii, 

 Quatrefages ; E. tiimida, Quatref. ; E. Beautempsi, Quatref. ; E. 

 callimorpha, Gosse ; Halcampa chrysanthelluni, Peach ; Peachia 

 tirulata, Gosse; P. triphylla, Gosse; Anemonia sulcata, Pennant; 

 Aiptasia Co?<c7u', Cocks ; Actinia equina, \JixmQ; Metridiuni dian- 

 /7«t5, Ellis ; Cereiis 2>^diiyindatus, Tcunant ; Sar/artia nivea, Gosse; 

 S. viduata, Miiller (including S. troghdi/tes, Johnston) ; S. venusta, 



Ann. & Mag. N. Hist. Ser. 4. Vol. xv. 20 



