172 OLIGOCHAETA 



therefore, to that extent, diflFerent from, the female-ducts, graduate into them; the 



anterior pair of ducts in fact are longer than the second pair; the latter, it is 



true, are longer than the oviducts, but still they form a transition to them. The 



absence of spermiducal glands here seems to me to be really a primitive character. 



There are other facts, too, in the structure of the reproductive organs which argue 



in favour of the primitive characters of the Phreoryctidae ; I have pointed out 



elsewhere that in the embryo Lwmh'icus and Octochaetus there are four pairs of 



gonads, of which only three come to maturity; in certain species of Perichaeta 



there are two pairs of egg-sacs, corresponding to the presumably ancestral two 



pairs of ovaries ; now in Phreoryctes, at least in P. smithii, there are actually two 



functional pairs of ovaries and oviducts. The development of Octochaetus seems 



also to distinctly favour the view that the primitive form of generative duct is that 



which only occupies two segments; the external pore being on the segment following 



that which contains the funnel. In the development of that Annelid the ducts in 



question ran straight to the body -wall, and there ended ; how the further growth 



was effected I had no facts to enable me to judge. Besides, apart from the actual 



facts of development, the necessity of assuming an early correspondence between 



the male and female-ducts would lead to the assumption that the short male-ducts 



were the most primitive ; there is no Oligochaet known in which the female-ducts 



occupy more than one segment ; whereas there is every possible variation in the 



number of segments occupied by the male-ducts; this of itself makes it probable 



that the female-ducts represent the earlier condition. All arguments, therefore, appear 



' to me to point to the conclusion that Phreoryctes is, in respect of its reproductive 



organs, the most primitive type. The vascular system of the Annelid is also in 



a primitive condition, though not more so than that of the Tubificidae. The 



development of Lumbricus (Vejdovsky) shows that a perivisceral trunk in each 



segment of the body is the primitive condition; apart altogether from the facts 



of development, this would seem to be on a priori grounds likely; we know, too, 



that the reduced number of the commissural vessels in the Naids is derived from 



a more primitive condition, in which there was a perivisceral arch in each segment 



(see below). In this respect Phreoryctes is primitive; it is true that in one species 



of the genus, at any rate, the periviscerals are not continuous round the body ; but 



they are in P. smithii. 



There is no type in fact, in my opinion, which has such good claims to occupy 

 a low position among the Oligochaeta as Phreoryctes. It wiU be remembered also 

 that this genus is one which was placed by Lankestee in a position intermediate 

 between the ' Limicolae ' and the ' Terricolae ' of CLAPABiiDE ; it does undoubtedly 



