119 



that peculiar property of turning green on being preserved in alcohol, so 

 characteristic of the Clypeastroids. These facts, together with the characters 

 of the larva, decidedly indicate that Echinobrissus is related to the Cly- 

 peastroids, not to the Spatangoids, which, of course, apphes to the Cas- 

 sidulids in general. 



Brissus Agassizi Doderleini). 



FertiHzation of this species was undertaken at the Biological Station, 

 Misaki, on June 21st. The eggs are small and very clear, and the cleavage 

 is stated in my notebook 

 to be "ideally beautiful." 

 The gastrula stage was 

 reached at the age of 14 

 hours. The larva is a typic- 

 al Spatangoid larva, with 

 an unpaired posterior pro- 

 cess, not very long. At the 

 age of 7 days the postero- 

 dorsal arms had begun to 

 develop and the dorsal 

 arch had just appeared. 

 There is a prominent clust- 

 er of red pigment in the 

 point of the long and 

 slender postoral arms, and 

 also the posterior process 

 is red pigmented in nearly 

 its whole length. The larvae 

 were observed to swim 

 horizontally just beneath 

 the surface film. 



Although the larvae were kept alive until the 10th of July they did not 

 develop beyond this stage. Thus the important question whether postero- 

 lateral arms are present in this larva or not could not be settled, and the 

 character of the posterolateral rod, if present, remains unknown. The fact 

 that the basal prominences of the posterior rod do not show any sign of 

 prolongating upwards in the latest stages would seem to indicate that 



1) H. L. Clark (Hawaiian a. o. Pacific Ecliini. Echinoneidse . . . Spatangidse) regards 

 all the Pacific forms of Brissus, including the Panamic Brissus obesus Verrill, as one single 

 species, Br. latecarinatus (Leske). Not yet having had an opportunity of examining the 

 question myself, I prefer to keep for the present both the Japanese and the Panamic forms 

 under their separate names. 



Fig. 51. Skeleton of larva of Brissus Agassizi. A. from 

 the ventral side ; B. side view, ^'"/i- ^1- anterolateral rod ; 

 b. body rod; p. posterior rod; pd. posterodorsal; po. post- 

 oral; r. recurrent rod; vtr. ventral transverse rod. 



