138 Transactions. — Zoology. 



cup-shaped, with the concavity directed forwards, and in the 

 segments which contain the sperm-sacs and ovisacs this 

 concavity is much emphasized by the stretching of the septa 

 caused by the growth of the sacs in question. As far as I 

 am aware, Pelodrilus is the only instance of an Oligochaet 

 which Claperede would undoubtedly have referred to his 

 group of LimicolcB, where this increase in thickness of the 

 anterior intersegmental septa is met with. It may very 

 possibly have a relation to the habitat of the worm in 

 soil, and not in the softer mud at the bottom of a lake or 

 river, and in any case it shows that no importance can be 

 attached to the presence of these thickened septa in earth- 

 worms as a character distinguishing them from the lower 

 Oligochceta. In view, however, of other points in which 

 Pelodrilus resembles the higher Oligocholia, this character 

 perhaps gains an additional importance. 



" Septal Glands. — The septal glands are found in segments 

 v.-vii. : they form a series of paired structures lying on the an- 

 terior face of the cup-shaped septa which lie between these seg- 

 ments. I could not find any evidence of their possessing a central 

 lumen such as has been described by various writers. In all 

 my sections the septal glands were undoubtedly solid struc- 

 tures, though often furnished with a fibrous core. They have 

 a glandular appearance, and are pear-shaped. The structure 

 of these glands, in fact, is very much like that of the ' capsulo- 

 genous ' glands in Pericliata. In Pelodrilus I must confess 

 to having been unable to trace the ducts of the septal glands 

 through the pharyngeal epithelium. They appeared to end at 

 the bases of these cells. It is almost unnecessary to point 

 out that there is every probability of the pharynx being in 

 Pelodrilus of stomodseal origin. 



" Testes. — There are two pairs of testes, placed in seg- 

 ments x. and xi., and attached to the anterior septa of their 

 segments. They are of considerable size when fully developed, 

 and branched at their free extremities. In the mature worm 

 the testes are nearly always incomplete in number, owing, pre- 

 sumably, to the fact that the germinal cells of one or more of 

 the gonads have been transferred to the interior of the sperm- 

 sacs. 



" Vasa Deferentia. — The vasa deferentia are remarkably 

 long and greatly coiled. The vas deferens is for the most part 

 extremely thin, though it widens out just before joining the 

 funnel, and also for some little distance in front of the ex- 

 ternal orifice. In the extremely thin and much-coiled vasa 

 deferentia, Pelodrilus differs from all the Oligochceta, to which 

 it presents other points of affinity. The structure of the 

 vasa deferentia is not in any way peculiar ; they are, as is 

 always the case, composed of a single layer of cubical cells, 



