4 MR FRANK E. BEDDARD ON THE 



§ 2. Body- Wall. 



The chief fact to be noticed with regard to the body- wall is the much greater thickness 

 of the anterior segments. Figs. 3 and 4 are drawn to scale, and show that in the front 

 part of the body the total thickness of the body- wall is quite double that of the segments 

 further back. 



Attention has been called to this fact by Perrier, who has suggested that this anterior 

 region may function as a clitellum ; as the clitellum in Moniligaster has been discovered 

 by Bourne [6], this is not perhaps very likely, and besides I do not find any difference in 

 minute structure between the epidermic covering of the anterior and posterior segments ; 

 the former may perhaps be a little thicker, but that is the only difference. Furthermore, 

 at the hinder end of the body, the thickness of the integument was almost if not quite as 

 great as that of the anterior segments. 



The characters of the epidermic cells do not differ from those of other Oligochseta. 

 Large glandular cells with granular contents are separated from each other by fine 

 "packing" cells. 



A point of importance is that the epidermis is vascular; capillary loops penetrate 

 between the epidermic cells, as is now known to be the case in many Oligochseta, especially 

 among earthworms; in fact, since the vascularity of the integument in the Oligochseta 

 was first pointed out by myself [5] in Megascolex caruleus, many of the principal 

 genera have been shown to share this peculiarity; even among the Limicolse the pene- 

 tration of blood capillaries into the epidermis is not unknown, but the thinness of the 

 integumental layers among these smaller Oligochasta is no doubt responsible for the very 

 slight degree in which the body-walls are supplied with haemal vessels. 



§ 3. Alimentary Canal. 



The mouth leads into a buccal cavity, which is as usual defined posteriorly from the 

 pharynx by the fact that the cerebral ganglia are placed in the interval between the two ; 

 as the cerebral ganglia lie between the third and fourth segments, the buccal cavity may 

 be said to occupy the first three segments; it will be remembered, however, that the two 

 first segments together are hardly equal in antero-posterior diameter to the third ; hence 

 the actual space occupied by the unimportant buccal cavity is not great. 



The pharynx appears to occupy all the remaining space before the first thick mes- 

 entery, i.e., two segments, Nos. IV, V. But as there is a considerable length of oesophagus 

 also packed away in this space the pharynx must, I think, be considered to occupy only 

 one segment, the IVth. In papers dealing with the anatomy of Oligochseta, the pharynx 

 is often spoken of as occupying four or five segments; and this appearance is frequently 

 presented by a dissection of the fore end of the body. But in many of these instances 

 at least the pharynx itself really occupies a more limited space ; its large size has caused 

 the pushing back of that portion of the oesophagus which immediately follows it. There 

 is nothing particular to say about the minute structure of the pharynx. 



