288 



J. H. ASHWORTH. 



Table of Measurements of the Siplionozooifls of 

 Heteroxenia Elizalietliae. 



By meaus of their rudimentary, short, rounded tentacles 

 the zooids may be readily distinguished from young polyps of 

 the same size, whose tentacles are longer, pointed, and bear 

 pinnules. Compare, for example, the young polyp A 5 (see 

 table, p. 287) with the siphonozooid S 5. They are both about 

 the same length, but the tentacles of the former are 1'3 mm. 

 long, and, examined from outer aspect, show seven pinnules 

 on each side of the middle line, whereas the tentacles of the 

 siphonozooid are only '2 mm. long, and are simple rounded 

 lobes. Now if, as urged by Schenk and others, these two 

 individuals are both young polyps, how can the differences in 

 the size and character of their tentacles be accounted for? 

 If the zooids are stages in the development of polyps, it is 

 very difficult to account for so many being in the same 

 stage of development (as the tentacles of all the specimens 

 examined are in the same simple condition), when, on the 

 same colony, other individuals of the same length, or even 

 smaller, have already acquired some of the adult characters, 

 viz. the pinnate tentacles. On the colony drawn in fig. 37 

 there are over two hundred zooids, all of which are similar in 

 appearance, having simple round tentacles. The examples 

 indicated in the above table are chosen haphazard from this 

 large number, being arranged in order of length merely for 

 couvenieuce of reference. If these were young polyps we should 



