M/vLACOZOA. APODA. HETEROBRANCHIATA. o\3 



the ventral portion white, more or less dotted witli yellow and 

 scarlet, or tinged with blue. The tubes short, the upper eight- 

 lo])ed, the lower six-lobed. The ridges do not nui far down 

 the tubes, and the rest of the sac is plain. The branchial 

 cavity extends to the base of the sac, and is lined by a delicate 

 membrane, generally of a scarlet colour, beautifully reticulated 

 with whitish filaments crossing each other and having promi- 

 nent papillre at the intersections. The oesophagus very short, 

 the stomach very large, ovato-globose, the intestine very wide, 

 sigmoid, of a brown colour when filled, otherwise whitish ; the 

 inner surface of the intestinal canal villoso-papillate. 



This species, although the individuals vary in form, does 

 not in individuals present much variation, the external sac 

 being rigid and little capable of extension. It is easily dis- 

 tinguishable by the hyaline appearance of the outer sac, through 

 which the bright red of the inner is apparent. 



Abundant in deep water, off Aberdeen, adhering to dead 

 shells, stones, agglutinated sand, and the like. Corallines, 

 small shells, and other bodies, often adhere to it, and Modiola 

 discors is sometimes found imbedded in its outer coat. 



3. Ascidla intestbidUs. Intestinal Ascidia, 



External sac subovate when contracted, and somewhat com- 

 pressed, oblong or subcylindrical when extended, softish, rugose 

 or even, smooth, transparent, hyaline, greenish-grey, or bluisli- 

 green, composed of a dense fibrous external layer, numerous 

 thinner cellular laminae, and an inner subgelatinous transparent 

 layer. It is terminated above by two short tubes, the upper 

 larger eight-lobed, the lower six-lobed. The free internal space, 

 filled with water, is very large, but the fluid also occupies the 

 gelatinous cellular tissue, which forms the inner membranes of 

 the outer sac. The latter is thin, so transparent that the organs 

 can be easily seen through it. In the ordinary state this sac 

 is ovate, narrowed above ; but when contracted, its upper part 

 is cylindrical, narrow, longitudinally furrowed, transversely 

 rugose, and terminates in two contractile tubes placed near 

 each other, the upper longer, with eight grooves, and having 

 at the aperture a bright yellow margin folded into eight lobes, 

 on the middle of each of which externally is a bright red spot, 

 sometimes prolonged into a ray ; the lower tube similar, with 

 six lobes and longitudinal grooves. Between the tubes is a 

 small hemispherical white glandular body. On being handled, 

 the animal contracts the external sac to less than half its 

 length, throwing it into transverse ruga?. An individual lived 



2d 



