CRANGON VULGARIS. 151 



adult Crangon the mandible is bent at right angles and ter- 

 minates in a toothed occludent surface but is not provided 

 with a palpus. In the embryo at stage If, the mandible 

 has much the appearance of the adult (fig. 24) but it pos- 

 sesses, besides, a prolongation from the outer lower angle 

 which I am inclined to regard as a mandibular palpus 

 though in its bifid termination it is unlike any palpus with 

 which I am acquainted. I was unable to ascertain whether 

 it were freely movable upon the mandible or not. 



The last figure upon the plate (tig. 27) represents the 

 shrimp after escaping from the egg, a stage which may be 

 designated by the letter /. With this the shrimp passes 

 beyond the scope of my inquiries and the figure is intro- 

 duced so as to connect my series with the later larva of 

 Clans ('61). Glaus represents a form which he believes 

 to be the young of Crangon ; but his figure depicts a more 

 advanced stage than mine for it has an additional pair of 

 thoracic appendages while the caudal fin is formed by the 

 outgrowth of the pleopoda of the penultimate abdominal 

 segment. There are also differences to be noted in the 

 shape of telson and the relative lengths of its marginal 

 spines, the size and development of the antennae and anten- 

 nulae as well as in other points. 



To be continued. 1 



1 The bibliography will be given with a succeeding portion of the present ar- 

 ticle. The references to it iu the text are given in full face type which indicate the 

 date of each article. 



