175 



ventral plate; it is not formed in all the radii; I find it present sometimes 

 in three radii, sometimes only in two or one, but not in more than three 

 radii in any of the specimens available. — 



In fig. 96 part of a young specimen, 12 days old is represented. The 

 second pair of lateral plates has begun to form; the inner (in reaUty the 

 second) ventral plate has assumed an elegant hourglass-shape. The buccal 

 plates have not yet been formed. Inside the ventral plate a pair of small, 

 irregularly halfmoon-shaped plates has appeared, representing the adoral 

 plates. (This interpretation is not in conformity with that usually adopted; 

 I cannot, however, enter here 



on a discussion of the mor- - /'.•f~'\ to 



phology of the oral skeleton 

 of Ophiurids). 



When the young Ophiurids 

 had reached this age, the so- 

 journ at Tobago ended and 

 put a stop to the experi- 

 ments, and the few speci- 

 mens left were preserved. But 

 I cannot have the slightest 

 doubt that it would be very 

 easy to rear the young Ophi- 

 urids of this species to a much later stage, since it is very easy to give 

 them suitable conditions. The species is found in quite shallow water on 

 the coral reef, in the sand under old coral blocks, together with a number 

 of other species of Ophiurids. The experiments carried out thus far indicate 

 that here is a lot of interesting work to be done. 



Quite recently a notice on the development of another species of Ophio- 

 nereis, 0. Schayeri (M. Tr.), was published by H. B. Kirk^) indicating the 

 highly remarkable fact that in this species the development is absolutely 

 direct, no larval form apparently occurring at all, the young star forming 

 already within the tough envelope by means of which the eggs are attached 

 to the under surface of stones. Unfortunately, the identification of the 

 species is not beyond doubt, the deposition of the eggs not having been 

 observed and the young Ophiurids not having been reared until they could 

 be identified with certainty. 



It would be exceedingly interesting to study the development also of 

 other species of this genus; although thus (probably) two species of the 

 genus have been shown to develop without the Pluteus larval stage, it is 



^) H. B. Kirk. On the much-abbreviated development of a sand-star {Ophionereis Schay- 

 eri). Preliminary Note. Transact. & Proc. New Zealand Inst. Vol. XLVIII. 1916. p. 383—384. 



Fig. 96. Part of a young Ophionereis squamulosa, 12 

 days old. ad. adoral plate; p. mouth papilla; t. tube- 

 foot; to. torus angularis; v. ventral plate, ^^"/i. 



