278 CRUSTACEA. 



latter, uulike that of ylstacus, has no fringe of setae. Development seems 

 still more abbreviaterl than in Astacus, inasmuch as the caudal fin very soon 

 attains conij^letion. 



E. Loricata. 



The larvae of the Loricata hatch in a form loner known as the 

 Pliyllosoma, which was formerly regarded as an independent genus 

 and placed either among the Stomatopoda or among the Decapoda. 

 That this form belonged to the ontogeny of the Loricata Avas first 

 rendered prohahle liy the experiments in cultivating specimens 

 made by Couch (No. 116), who was able to hatch, from the eggs 

 of Palirainis, larvae which Gerstacker had already a.ssumed to lie 

 PhyllosomK. Coste and Gerbe arrived at the same results almost 

 simultaneously. The embryonic development of Scyllartis and 

 Palinunis, as Avell as the transition into the young Phyllosoma, 

 Avas made known by Dohrn (No. 119), while the metamorphosis of 

 the Phyllosom'i Avas established chiefly by Glaus (Nos. 91 and 8) 

 and RiCHTERS (No. 146). A-^arious Phyllosoma have recently been 

 described by S pence Bate (No. 100). 



The PliyllosoiYia must be regarded as a peculiarly-shaped My sis 

 stage. The Loricata thus leave the egg at the stage at which many 

 of the Astacidea hatch. The leaf-like, flatly compressed shape of 

 the body and the slight development of the abdomen must be 

 regarded as adaptations to a pelagic existence, Avhile, on the other 

 hand, apparently primitive characters are retained in the independence 

 of the thorax and tlie presence of f ureal processes on the telson. 

 Other features, hoAvever, can only be explained as degeneration- 

 l)henomena, the correctness of this view being confirmed by com- 

 parison with the embryonic stages. 



The embryos of Scyllarus, Avhose ontogeny Avas Avorked out by 

 DoHRX, pass through a Naupllus stage Avhich bears a general re- 

 semblance to that described above (p. I.'i6) for Astacus, and is marked 

 by the secretion of a larval integument (Nauplius cuticle). The 

 later stage also resembles the corresponding stage of Astacus, in 

 that the posterior I'egion of the body Avhich has noAV developed 

 (thoraco-abdomen) appears flexed ventrally. The anterior region of 

 the body, in Avhich the food-yolk is deposited, bears the tAvo pairs 

 of antennae and the mouth-parts, including the first maxillipedes. 

 The second and the third maxillipedes are found on the recurved 

 thoraco-abdominal section, together with the rudiments of the three 

 anterior ambulatory limbs. Behind the last pair of these rudi- 

 ments there folloAvs an unsegmented terminal region in the form 



