E. MARSIIALLI. — YOUNG SPECIMENS. 109 



The beams are at places about Y3 mm. broad, but for the most 

 part are exceedingly fiue. 



Specimens of over 60 mm. in length of body show a well 

 arched sieve-plate, which is of sufficient strength to remain intact 

 in most cases. For instance, the specimen of fig. 9 (63 mm. 

 long) has a complete, vault-like sieve-plate with about 35 meshes. 



As to spiculation of young specimens, I have, in the first 

 place, subjected a portion of the youngest specimen I have had 

 (18 mm. long) to a careful examination. The dermalia were found 

 to be sword-like hexactins like those of adults. I mention this 

 because in Regadrella okinoseana I have found the dermalia in 

 quite early postembryonal stages to consist of pentactins which 

 are later replaced by hexactins (see under that species). In the 

 absence of parietal oscula, the oscularia are certainly not devel- 

 oped. It is noteworthy that, although both floricomes and 

 graphiocomes were common and even that rare form of hexasters 

 shown in fig. 21, PI. IV, was met with in a few instances, yet 

 I failed to discover a single oxyhexaster in that little specimen. 

 The floricome (62-72 ij. dia.) was on the average smaller and its 

 terminals somewhat more slender than in adult individuals. 

 Rhaphides detached from the graphiocome were already present 

 in the superficial region, though by no means yet in great pro- 

 fusion. 



Of the spiculation in other young specimens I will make 

 only the following remark. The oxyhexaster was sought in vain 

 or was met with exceedingly rarely in preparations made from 

 several individuals under 60 mm. in length of body. From about 

 the period of the body-length just mentioned and onward, the 

 oxyhexaster begins to be constantly seen, though not in abun- 



