sovie nein Species o/Drawida. 501 



the narrow ciliated tubules are considerabl}^ wider than in 

 the nephridia of the hinder somites. The whole SA^stem of 

 drainiug- tubes is connected by fairly M'ide vertical canals 

 and is a device for tlie rapid absorption and diffusion of fluids 

 into the pharynx. It is doubtful whether, at least in this 

 genus and others affecting the hotter coiintries, the term 

 salivary gland used in certain text- books for the description 

 of these nephridia, correctly denotes their function, which at 

 any rate cannot be peptic. At least in the several species 

 of Drawida which I have observed and examined, these 

 structures would appear to be associated more with the 

 function of collecting and discharging Avater through the 

 mouth, both while feediug and burrowing, than with any 

 digestive function. 



h\ the species of D. elegans and D. viodesta described 

 below, the intestinal appendages, chieily in the posterior 

 somites, are greatly enlarged, while the blood-vessels going 

 to them on either side, are also correspondingly elongated. 

 Usually a supra-intestinal ('? typhlosolar) vessel is found in 

 these forms, and the appendages in such cases have a double 

 connection with the vessels — one with the dorsal and the 

 other with the supra-intestinal vessel. The enteric vessel 

 is derived in an arbitrary manner, either directly from the 

 longitudinal vessels or from the appendicular branch. 



At the same time, these appendages in the several somites 

 are more or less confined to one border of the branch-vessel, 

 and developed in the form of separate lobes. It is hypo- 

 thetiealiy possible to derive the recently described septal 

 nephridia of Pherethua posthuma from the enteric appendages 

 of Draivida, and the only fact available at present in favour 

 of such a hypothesis is the histological resemblance between 

 the two structures. The excretory water-conserving organs 

 o^ Draivida are certainly mesoblasiic in origin, as is testified 

 to by their cellular structure, and for a similar reason the 

 septal nephridia also are of the same origin'^. Moreover, 

 there is not any histological difference between the septal 

 organs of Pheretima and the nieso-nephridia of genera like 

 Acanthodrilus, Perlchceta, Megascolex, Netoscolex, and other 

 forms which I have investigated. The process of the 

 evolution of septal nephridia may be illustrated as shown in 

 text-tig. 2. I am disposed to believe that the suggestion 

 of Dr. Woodland that the system of enterouephric tubules 



* 1919. N. F. Woodland, Q. J. M. Sci. n. s. vol. Ixiv. part 1, p. 101. 

 "But it seems to be evident that the septal nephridia of Iherelima 

 certainly cannot be developed from ectoderm, but must be mesodermal iu 

 origin, since we can hardly suppose they are endodermal outgrowths. 



