SYSTEMATIC POSITION OF A GIGANTIC EARTHWORM. 69 



On the opposite side of the body an exactly equivalent series of pouches is present. 

 I have ascertained by transverse sections that these structures are, as is stated, caecal 

 pouches opening on to the exterior of the body. 



A second individual of this Earthworm, which was acquired by Mr. Bartlett, and 

 lived for a short time in the Society's Gardens, showed some slight variation in the 

 number of these pouches. On the left-hand side of the body the first segment has 

 two, the second four, one being in reality double, the third and fourth segments three 

 each. On the right-hand side of the body the first segment had two of these pouches, 

 the two next three, and the last two. These variations are not, however, of any 

 importance, I should imagine. 



These structures are not peculiar to Microchceta, but are represented in a species of 

 Periclicda. In Perichceta asjiergillum M. Perrier' figures a series of small accessory 

 bodies developed in the neighbourhood of the copulatory pouches, and I have repro- 

 duced in fig. 7 of PL XV. M. Perrier's drawing in order to display the close resemblance 

 between the two sets of structures ; there can be little doubt that they correspond to each 

 other, and their development in connection with the copulatory pouches in one 

 worm and the segmental organs in the other is, at least, an indication of an homology 

 between these latter, an homology which is undoubtedly suppoi'ted by other facts. 

 In any case the very close similarity between the copulatory pouch of Perichceta (fig. 7) 

 with its accessory pouches, and the segmental organ of Microchceta (fig. 6) with a 

 corresponding series of accessory pouches, is worth remarking as a curious coincidence, 

 if no more. 



It must also be remembered that true copulatory pouches like those of other Earth- 

 worms are absent in Microchceta, though their function is probably taken on by the 

 structures already described ; and it is not at all likely that the copulatory pouches, 

 were they present, would have escaped attention in two separate individuals, since they 

 are so extremely conspicuous in other Earthworms, even in immature individuals. It 

 is possible that the correspondence between the copulatory pouches and the nephridia 

 of Earthworms is only partial, that is to say, that the nephridia and the copulatory 

 pouches are both derivable from a segmental organ like that of Microchceta with a large 

 diverticulum. This hypothesis would explain several of the difficulties which beset the 

 question of the homologies between the two structures ; it might for instance account 

 for the presence of a segmental organ and a copulatory pouch opening close together 

 upon the same series of setae in Urochceta. Furthermore it is possible that the small 

 diverticulum of the copulatory pouches found in so many species of Perichceta (see 

 fig. 7, PI. XV.) is a rudiment of a nephridium opening in common with it as in 



' For a disouBsion of the homologies between the segmental and the ducts of the generative system, including 

 the copulatory pouches, see Laukester, Quart. Journ. Jlicr. Soo. 1864 ; Perrier, Arch. d. Museum, 1872, and 

 other memoirs already cited. 



