3 oo 



THE CRUSTACEA 



the uropods are the last to appear. In Nephrops (Fig. 177) the 

 course of development is very similar, but the larvae are 

 distinguished by the long spines of the abdominal somites and 



telson. The freshwater Cray- 

 fishes have a direct develop- 

 ment, the young on hatching 

 resembling the adult in most 

 points, but lacking the first 

 and the last pairs of abdominal 

 appendages. 



The Scyllaridea have a 

 very peculiar and character- 

 istic series of larval forms, 

 which were long described as 

 adults under the generic name 

 Phyllosoma (Fig. 178). These 

 larvae are remarkable for the 



r American Lobster (Homarus ameri- l ar cr e s i ze to which SOHIC attain, 

 Scmzo pod-stage, o , antennule ; a , y .. . , a 



' maxiiiiped ; pt-p*, the five and for their extremely flat- 

 ith ' fr ' tened and leaf-like form and 



glassy transparency. The body 

 is sharply divided into three regions. The first, which is covered 

 by the oval carapace, includes the head and the first two thoracic 

 somites. The remainder of the thorax forms a discoidal plate and 



FIG. 17 



Larva of 

 conus), in 



antenna ; mf", third 

 pairs of legs. (Afte 

 schelt and Heider's Embryology.) 



A 



PIG. 177. 



Late Schizopod -stage of Nephrops norvegicus. a', antennule ; a", antenna ; mf", third 

 maxiiiiped ; p^-p 6 , the five pairs of legs ; pi' 2 , p&, pleopods ; r, rostrum. (After Sars, from 

 Korschelt and Heider's Embryology.) 



is followed by the narrow and indistinctly segmented abdomen. 

 The last two thoracic appendages are not developed in the newly 

 hatched larva, but the four pairs in front of them are long and 

 slender, with natatory exopodites. The first thoracic limbs are 

 rudimentary (Palinurus) or absent (Scyllarue), and the second pair 



