POST-PUEKULTjS STAGE OF JASL'S LALAN1H1. 



J93 



many showed, on closer examination, a varying number of small additional 

 spines, and a few, many more than in any of the three accounts. The 

 meaning of this became apparent when the specimens, which had been reared 

 to the post-puerulus stage, were examined, and it was possible to compare 

 the cast cuticle of the puerulus stage with the new cuticle of the stage 

 following. The cast cuticle, when examined by a lens, showed only the fifteen 

 spines, as originally described, while the new cuticle showed many more. 

 These had not of course appeared suddenly, and the apparent presence of a 

 varying number of additional spines, more or less distinct, in most of the 

 pueruli, is due to the presence of spines arising under the old cuticle, but not 

 affecting it. To make quite certain that there were no additional spines 



Fig. 3. — Spines of carapace of post-puerulus. Spines of carapace of puerulus. 



card., cardiac ; fr. 1, frontal ; fr. 2, small spine behind it ; gast., gastric or post-orbital ; hep., 

 hepatic; inf. br., first inferior branchial; metl. gast., median gastric; sup. br., first 

 superior branchial. 



even in the form of obtuse projections of the cuticle, it was examined in all 

 positions by a lens. The cuticle of the post-puerulus stage was then removed 

 from the body and examined microscopically along with the cast cuticle. 

 Figs. 3 and 4 are camera lucida drawings of the two, showing the general 

 arrangement and number of the spines. It will be seen that three of the 

 spines in the puerulus are merely slight elevations of the cuticle, namely 

 the median gastric and the single pair of cardiacs, all the others being well 

 developed and with sharp points. The cardiacs alone had a few setje. The 

 cuticle of the post-puerulus, on the other hand, had all the prominent spines 



