76 



ASCIDIANS 



" Challenger " expedition ; eight or nine species are now known 

 from various parts of the world, ranging in depth from 630 to 

 2425 fathoms. Most of the species are from the Pacific ; only 

 one from the North Atlantic. The curiously curved type of 

 spicule found in the branchial sac and other organs is shown at 

 Fig. 50, C (p. 87). 



Amongst the Cynthiidae are found most varied conditions of 

 the reproductive organs. The gonads are sometimes on both, some- 

 times on only one side of the body, sometimes in one or several 



Fig. 39. — Various Cynthiidae. A, two forms of Styelopsis grossxilaria, Van Ben. ; B. 

 Forbesella tesseUata, Forb. ; C, Polycarpa aurata, Q. and G. ; D, Styela clava, 

 Herdman ; E, Polycarpa tinctor, Q. and G. ; F, Cynthia formosa, Herdman ; G, 

 Polycarpa comata. Alder ; H, Polycarpa pedata, Herdman ; I, Pelonaia coiTugata, 

 Forb. and Goods. (After Herdman.) 



branched masses, and sometimes distributed as a large number 

 of minute " polycarps " over the inner surface of the mantle. 



The family Cynthiidae is the largest section of the Simple 

 Ascidians. The species range from the size of a pea to that of a 

 large cocoa-nut. They are for the most part opaque, and often 

 richly coloured — reds, yellows and rich browns predominating — 

 and so look very different to the grey gelatinous Ascidiidae, and to 

 the sand-encrusted Molgulidae. They extend from between tide- 

 marks {Shjelojjsis grossularia), down to the abysses {Shjela hythia 

 and S. squamosa at 2600 fathoms). Some genera {Styela and the 

 closely related Denclrodoa), extend far into Arctic seas, but many 

 allied forms {Styela and Folycarpa) are also found in the tropics. 



