42 



and truncated posteriorly; the postoral rods are simple, and the body 

 skeleton forms no basket structure (Fig. 9). The branches at the end 

 of the body rod, as also the recurrent rods are rather strongly thorny 

 dstTnctly more o than in the larva of L. anamesus. The larva is very 

 trfnspaL, with a small cluster of red pigment cells in the point of each 

 arm and a few cells of the same colour spread irregularly in the body. 



At the age of 11—12 days the larv« showed the beginnmg 

 formation of the vibratile lobes; after this they did not develop 

 any further and soon died. I can thus give no information 

 about the shape and skeletal structure of the fully formed 

 larva. Especially it would be important to know whether 



Fig. 9. Skeleton of the larva of Lytechinus panamensis. A. front view; B. side view, '""/i- 

 Letters as in fig. 5. vtr. ventral transverse rod. 



epaulets and the posterior transverse rod are present (as is to be ex- 

 pected) or not. But, anyhow, the fact here made known that the larva 

 in its first stage is in perfect accordance with that of L. variegatm and 

 anamesus (+ pidus) is of considerable interest. 



Lytechinus verruculatus (Ltk.) 



In the beginning of April 1915 1 undertook repeatedly fertilization of 

 this species during my stay at Hilo, on the island of Hawaii. 



The eggs are small (1 have no measurement of them) and very clear. 

 The cleavage proceeds at an extraordinary speed, so that already four 

 hours after fertihzation the blastula stage is reached (though not yet 

 swimming); the embryos are very transparent and form an excellent 

 object for microscopical study. The first larval stage has the usual shape, 

 with the posterior end short and truncated. The body skeleton forms 



