278 CRUSTACEA. 



latter, unlike that of Astacus, has no fringe of setae. Development seems 

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

 attains completion. 



E. Loricata. 



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

 Phyllosoma, 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 was first 

 rendered probable by the experiments in cultivating specimens 

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

 of Palinurus, larvae which Gerstacker had already assumed to be 

 Phyllosoma. Coste and Gerbe arrived at the same results almost 

 simultaneously. The embryonic development of Scyllarus and 

 Palinurus, as well as the transition into the young Phyllosoma, 

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

 the Phyllosoma was established chiefly by Claus (Nos. 91 and 8) 

 and Kichters (No. 146). Various Phyllosoma have recently been 

 described by S pence Bate (No. 100). 



The Phyllosoma 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, while, on the other 

 hand, apparently primitive characters are retained in the independence 

 of the thorax and the presence of furcal processes on the telson. 

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

 phenoniena, the correctness of this view being confirmed by com- 

 parison with the embryonic stages. 



The embryos of Scyllarus, whose ontogeny was worked out by 

 Dohrn, pass through a Naupllus stage which bears a general re- 

 semblance to that described above (p. 156) 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 region of the body which has now developed 

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

 the body, in which the food-yolk is deposited, bears the two pairs 

 ntennae and the mouth-parts, including the first maxillipedes. 

 second and the third maxillipedes are found on the recurved 

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

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

 ments there follows an unsegmented terminal region in the form 



