184 



reasonable certainty on preserved specimens, whether the differences 

 really are of clasificatory value or only due to different age, I prefer 

 to describe all the specimens as the same species, and in the 

 description of the single characters to point out the local differences. 



As to the size of Synaptula hydriformis Clark writes (The 

 Apod. Holoth. pag. 82) that it is 10 — 15 cm. None of the specimens 

 at hand are so large. The largest specimen at hand, one of those 

 from Jamaica, measures 7 cm and another measures 6 cm. The 

 other specimens from Jamaica are 3 — 3 l /s cm long, while 0rsted's 

 specimens from St. Croix are but 0,8 — 1,5 cm long. The specimens 

 from Tobago vary from 0,4 — 1,5 cm and those from Bermuda from 

 1 — 3 cm. These differences in size may probably be due to 

 differences in age alone; but as the different groups are from 

 often widely different localities, and the larger part of them have 

 embryos in the body-cavity, it cannot be regarded as certain that 

 age alone accounts for the different sizes. Besides no other Synaptula 

 is known where the size of the mature specimens varies to such 

 extent. 



The large specimens from Jamaica are pure white, but whether 

 they are really white, or their colour has disappeared in alcohol it 

 is not possible to see. All the other specimens, excepting alone 

 0rsted's which have lost their colour, are either green or reddish. 

 That the lacking of colour in 0rsteds specimens is due to fading 

 is seen from his figures cfr. Pl. Ill, which represent them as green 

 and reddish. In balsam preparations it is seen that the green 

 colour is due to green chromatophores, and that the red colour is 

 diffusely spread all over the body. As furthermore the red speci- 

 mens have also green chromatophores, there is reason for supposing 

 that hydriformis is normally green, and that the red colour is due 

 to their eating spores of red algae. 



In mature specimens there are always 12 tentacles. They are 

 united at the base, and each has up to 20 pairs of digits. The 

 digits are not united by a web, and are placed at distinct intervals 

 cf. (Fig. 23. 1). On the oral disk there are twelve pairs of large 

 eye-spots. In one of the specimens from Bermuda, there are beside 

 the normal eyes on the oral disk several large eye-spots on the digits. 



The calcareous ring (Fig. 23. 6) is weak and nearly quite en- 

 closed in the cartilaginous ring. It is usually pure white and has 



