1890.] WORMS OF THE GENUS PERICH^TA. 67 



The spermathecce, 4 pairs, present nothing remarkable in their 

 structure ; each is a small pear-shaped pouch with a single small 

 stalked diverticulum. 



The sperm-sacs have a somewhat peculiar structure which is 

 illustrated iu fig. 10. In segments 11 and 12 are a pair of oval 

 sacs ; those of each side of the body are connected with each other, 

 but there is no contact between the sacs of the right and left sides 

 ventrally ; from each of the oval sacs is a small projecting tube- 

 like outgrowth {x, Plate V. fig. 10), which in the dissected worm 

 appeared to be broken off at its extremity. 1 am inclined therefore 

 to suppose that there is a connection above the intestine between 

 the two sperm-sacs of each segment by means of these outgrowths ; 

 if so, there is a striking resemblance in this particular between Peri- 

 chcsta vaillanti and Dichogaster, in which worm I have figured 

 and described (10) an almost identical arrangement. 



The ovaries are in segment 1 3, attached to the anterior mesentery 

 of this segment. 



The oviducts are perfectly normal. 



The atrium is again rather unusual in its structure ; as a general 

 rule that portion of it which lies nearest to the external orifice has 

 thickened muscular walls and is curved upon itself like a horseshoe ; 

 its calibre gradually increases towards the external orifice. 



In Perichceta vaillanti the terminal portion of the atrium abruptly 

 widens to form an oval, thick-walled sac, as in P. inclica (Horst, 16), 

 into which the thin tube-like proximal part of the atrium opens. 



The only species with which the present could be confounded is 

 P. modigliani (Rosa, 25) ; but it differs from that species in having 

 no thick mesenteries and apparently in the structure of the sperm- 

 sacs. There is no knowing whether P. vaillanti is the same as 

 P. Juliana (Perrier, 19) ; the only fact known about the latter 

 species is that it has four pairs of spermathecae. 



List of Memoirs cited. 



1. Baird, W. — Description of a new Species of Eartliworm 



(Megascolex diffringens), found in North Wales. P. Z. S. 

 1869, p. 40. 



2. Beddard, F. E. — On the Anatomy and Histology of Pleuro- 



cheeta moseleyi. Trans. Roy. Soc. Ediub. vol. xxx. (1883), 

 p. 481. 



3. Beddard, F. E. — On the Anatomy and Systematic Position 



of a Gigantic Earthworm (Microchceta rappi), from the Cape 

 Colony. Trans. Zool. Soc. vol. xii. pt. 3 (1886), p. 63. 



4. Beddard, F. E. — On the genus Megascolex of Templeton. 



Ann. & Mag. Nat. Hist. May 1884, p. 398. 



5. Beddard, F. E. — Descriptions of some new or little-known 



Earthworms, &c. P. Z. S. 1886, p. 298. 



6. Beddard, F. E. — Observations on the Structure and Cha- 

 racters of certain new or little-known Earthworms. Proc. 

 Roy. Soc. Edinb. vol. xiv. p. 156. 



5* 



