200 PROF. J. D. F. GILCHRIST ON A 



I may add that though T have here spoken of a post-puerulus stage, this is 

 only for convenience. All such "stages" are artificial, and strictly there are 

 as many stages as there are ecdyses before the adult form is reached. 



Much remains still to be done before a fairly complete account of the early 

 stages of the Cape crawfish can be given. Thus, the transition from the 

 phyllosoma to the puerulus is not known, and the embryonic development is 

 untouched. The first will be a matter of a lucky haul of the nets, the 

 second is now being carried out. The material consists of stages from the 

 first formation of the blastoderm to the time of hatching. It has not yet 

 been completely examined, but I may state in connection with the present 

 paper, that the nauplius stage in the egg was found to occur forty-two days 

 before the time of hatching and setting free of the first larva. 



Summary. 



1. Several pueruli of Jasus lalandii have been kept alive to succeeding or 



post-puerulus stage, which shows the following changes : — 

 a. The red spots on the underside of the body disappear, and the whole 



of the upper parts become coloured. 

 h. The spines of the carapace (of a definite number in the puerulus) 



become much more numerous. 



c. The antennules lose the antennular screen of the puerulus. 



d. The mandibles resemble those of the puerulus in having three teeth, 



but differently disposed, and a cutting-edge has appeared. Denticles 

 appear between and on the first two teeth, as well as along the 

 cutting edge. The palp has become three-segmented. 



e. The exopodites of the pereiopods have disappeared. 



/'. The exopodites of the third maxillipedes are longer, by the addition 



of a flagellum. 

 p. The cervical groove is well marked at the sides of the body. 

 h. The pleopods have become smaller, especially the endopodite, which 



is now devoid of setae ; the coupling hooks and seta of the appendix 



interna have disappeared. 

 i. The telson has additional spines. 



2. The post-puerulus differs from succeeding stages in the following 



respects : — 

 a. Cuticle uncalcified. 



h. The incisor part of the mandible is provided with denticles on the 

 margin of its thick cuticle. 



c. The pleopods show no sexual differentiation. 



d. The third maxillipedes are separated at their bases. 



3. The occurrence of a naupliosoma stage has been confirmed in the New 



Zealand Jasus lalandii, and the phyllosoma and puerulus are similar. 



