50 



HISTORY OF CRUSTACEA. 



Chap. YII. 



lateral parts of the carapace may unhesitatingly be in- 

 dicated as the chief seat of respiration. They consist, 

 exactly as described by Leydig in the Daphnie, of an 

 outer and inner lamina, the space between which is 

 traversed by numerous transverse partitions dilated at 

 their ends; the spaces between these partitions are 

 penetrated by a more abundant flow of blood than 

 occurs anywhere else in the body of the Zoea. To this 



Fig. 17.3 



Fig. 18.4 



may be added that a constant current of fresh water 

 passes beneath the carapace in a direction from behind 

 forwards, maintained as in the adult animal, by a folia- 

 ceous or linguiform appendage of the second pair of 

 maxillae (fig. 18). The addition of fine coloured par- 

 ticles to the water allows this current of water to be 

 easily detected even in small Zoeae. 



3 Fig, 17. Zoea of a Marsh Crab (Cydograpsus ?), magn, 45 diam. 

 ■* Fig. 18. Maxilla of the second pair in the same species, magn. 

 180 diam. 



