m 



id. 



1.0, 



DESCRIPTION OF SPECIES 53 



is divided into two chambers by an expanded ring, and the mid-gut also has two chambers, the first 

 of which has a granulation on the walls. At its junction with the mid-gut the rectum has a pair of 

 small lobes as in other members of the family. The loop of the intestine is not twisted as in Poly- 

 clinic, and the post-stomach and mid-gut lie on the right side of the rectum as in Aplidium. The anus 

 has two lips, and lies about halfway along the length of the 

 branchial sac opposite the 7th row of stigmata. 



Post-abdomen. A narrow and very short neck joins the 

 post-abdomen to the abdomen. Below this neck the post- 

 abdomen swells to accommodate the gonads. The ovary (ov.) 

 lies near the anterior end of the post-abdomen and has a few 

 ova of various sizes. A few testis follicles lie anterior to the 

 ovary, but most of them are posterior to it (t). They are not 

 arranged in a single or double series as they commonly are in 

 Aplidium, but instead form, immediately below the ovary, a 

 wide mass which gradually decreases in thickness and passes 

 into the narrow posterior part of the post-abdomen as a single 

 series of follicles. The sperm-duct (s.d.) as it passes back over 

 the ovary divides into several smaller ducts which spread out 

 to the testis follicles. Below the level of the testis the post- 

 abdomen continues as a slender process which passes down- 

 wards inside the stalk of the colony for a distance of several 

 centimetres. This lower process is divided by a central septum 

 separating the two blood channels. The walls of the process 

 are provided with thin longitudinal muscles. Near the lower 

 end of the post-abdominal process there is often seen an 

 accumulation of cells containing reserve material. At its extreme 

 lower end is the heart, a simple U-shaped tube. 



Larva. Some zooids in one colony contained a few larvae 

 which unfortunately were not, I believe, fully developed. The 

 most advanced of these larvae measures about 0-7 mm. from 

 the end of the papillae to the base of the tail. There are three 

 anterior papillae, flanked on each side by a row of four rounded 

 ampullae. No epidermal vesicles are present at the stage of 

 development represented by these larvae. There is an ocellus 

 and an otolith. The tail when coiled round the larva reaches to 

 about the sensory vesicle. 



Remarks. With the exception of the atrial siphon which 

 opens directly to the exterior, all the characters of this 

 interesting genus indicate that it should be placed in the 

 subfamily Polyclininae. The existence of branchial papillae and 

 the form of the post-abdomen suggest a systematic position 

 closer to Polyclinum than to Aplidium. But it is separated 

 from Polyclinum, not only by the absence of common cloacal 

 cavities, but also by the presence of muscles on the wall of the post-abdomen. Protopolyclinum 

 probably branched off from the primitive Polyclinum stock after that stock had acquired its main 

 characters, but before all of them had been fixed as we know them in recent species. Thus the loss of 



Text-fig. 9. Protopolyclinum pedunculatum 

 gen.n., sp.n. (St. 934): Zooid. 



