66 HISTOEY OF CRUSTACEA. Chap. YIT. 



For some time, owing to an undue importance being 

 ascribed to the want of a particular branchial cavity, 

 Mysis, Leucifer, and Phyllosoma were referred to the 

 Stomapoda, which are now again limited, as originally 

 by Latreille, to the Mantis-shrimps (Squilla), the Glass- 

 shrimps (Erichthiis) and their nearest allies. Of the 

 developmental history of these we have hitherto been 

 acquainted with only isolated fragments. The tracing 

 of the development in the egg is rendered difficult by 

 the circumstance, that the Mantis-shrimps do not, like 

 the Decapoda, carry their spawn about with them, but 

 deposit it in the subterranean passages inhabited by 

 them in the form of th.in, round, yellow plates. The 

 spawn is consequently exceedingly difficult to procure, 

 and unfortunately it becomes spoilt in a day when it is 

 removed from its natural hatching place, whilst on the 

 contrary the progress of development may be followed 

 for weeks together in the eggs of a single Crab kept in 

 confinement. The eggs of Squilla, like those removed 

 from the body of the Crab, die because they are de- 

 prived of the rapid stream of fresh water which the 

 mother drives through her hole for the purpose of her 

 own respiration. 



The accompanying representation of the embryo of 

 Squilla shows that it possesses a long, segmented 

 abdomen without appendages, a bilobate tail, six pairs 

 of limbs, and a short heart ; the latter only pulsates 

 weakly and slowly. If it acquires more limbs before 



aucuppTTient comme les autres appendices, et parait avoir une autre 

 valeur morpliologique." 



