STUDIES ON EARTHWORMS. 81 



horse-shoe shaped bodies in the anterior region of somites xii, 

 XIII, XIV, XV. In the present species, as a rule, only four 

 spermathsecae are present ; a pair in each of the somites xi and 

 XII, and each is an elongated pyriforra sac (fig. 6) ; but in one 

 specimen an asymmetrical condition obtains, for here there 

 are, on one side, two pyriform sacs in each of the somites xi, 

 XII, while on the other side there is only one spermatheca in 

 each somite, one of which is crozier shaped (fig. 7). The 

 wall of the spermatheca is thick and muscular ; its internal 

 lining consists of tall columnar cells. In these two species 

 then we have a difference corresponding to that shown in 

 Perichseta aspergillum, E. P.,^ where there are numerous 

 small sacs (which, however, surround a larger one), and in P. 

 elongata, which has a simple large sac. It may be that as 

 the worm becomes more mature a larger number of sperma- 

 thecse will appear, for these specimens are apparently not quite 

 mature. If this were so it would certainly militate against the 

 theory of the homology between the spermathecse and a portion 

 of the nephridium. 



The nephridia closely resemble those of M. Rappi, but 

 their tubular portion is less developed, except in the case of the 

 first pair, where the coiled portion has a glandular appearance, 

 as in so many Earthworms, and may perhaps serve in some 

 way as a salivary gland though it has the usual nephridial 

 structure and an external aperture (see Darwin, ' Vegetable 

 Mould and Earthworms/ p. 42). The external pore of this pair 

 is situated, not on the anterior edge of somite ii, to which it 

 belongs, but on a slight prominence in somite i (fig. 2). 



In the vascular system ofM. Rappi, the dorsal vessel is 

 doubled in somites iv, v, vi, vii, viii, in the last of which the 

 walls are much thickened, so as to give a heart-shaped appear- 

 ance to the vessel. In M. Beddardi, there is the same con- 

 dition, but limited to somites vi, vii, viii. Beddard has noticed 

 a similar difl'erence in the extent of doubling of the dorsal vessel 

 in specimens of Ac. novse-zelandise," where usually the 



1 ' Nouv. Arch, de Mus. d'hist. nat. de Paris,' viii, 1872. 



2 'Proc. Zool. Soc.,' 1885, p. 821. 



VOL. XXVII, PART 1. NEW SER. F 



