53 



The dorsal arch has not yet been formed, and there is as yet no trace either 



of a posterior transverse rod. That this latter rod will prove to exist 



may be supposed from its existence in the two related forms described 



below, and especially in the larva from the Gulf of Siam, which probably 



belongs to T. toreumaticus. 



At the age of 12 days the larva had not developed beyond this stage, 



and as I had then to leave Misaki, there was no possibihty of studying 



its further development. I 



tried to carry the culture 



along with me; but while 



I succeeded in carrying 



some other cultures in good 



condition to Australia, this 

 one succumbed. 



In a plankton sample 

 from the Gulf of Siam (off 

 Koh Kam, 4. II. 1900) I 

 have found an Echinoid 

 larva which is so very 

 similar to the larva of 



Temnopl. toreumaticus^) 

 that it seems almost just- 

 ified to refer it to this 

 species. This larva is only 

 in a slightly more ad- 

 vanced stage than the 

 oldest stage of the T. to- 

 reumaticus larva reared. Vibratile epaulets are beginnmg to develop. 

 A posterior transverse rod has appeared and also the dorsal arch; on 

 the other hand the body rods have apparently not yet begun to be ab- 

 sorbed Posterolateral processes are indicated, which will be supported 

 by the branches of the transverse rod; that this rod has branches at its 

 ends can be seen, but their definite form is not yet to be ascertamed. 



1) The fact that this larva was taken in the beginning of February, wliile the tertilizations 

 were' undertaken in the end of June, does not render the reference of the -a to h.s speces 

 impossible, since some specimens taken off Koh Kong m the Gulf of Si^'" °" ^he 25th of 

 January 1900 prove to contain ripe sexual products. Whether this species has then a breeding 

 season^o long as indicated by these dates, or its breeding season is perhaps not so early in 

 Japan as farther South, remains to be ascertained. 



Fig. 16. Skeleton of larva of Temnopleums loreumalicus, 

 9 days old. '»7i. Letters as in fig. 5. dtr. dorsal trans- 

 verse rod. 



