ON HjEMONAIS LAUREN TIL 781 



REFERENCES TO LITERATURE. 



(1) Brutscher, K., "Mitteilungen liber die Oligochaetenfauna der Schweiz," Rev. Suisse de Zool., 



t. viii, 1900. 



(2) Michaelsen, W, "Ubereinige zentralamerikaniseh Oligochaten," Arch. f. Naturgesch., 78. Jahrg., 



Abt. A, 1912. 



(3) Stephenson, J., "Studies on the Aquatic Oligochaeta of the Punjab. Ill : On a species of Dero 



found in Lahore ; a contribution to the Dero question," Records I nd. Museum, vol. v, 1910. 



(4) " On a new species of Branchiodrilus and certain other aquatic Oligochaeta, with remarks on 



cephalisation in the Naididse," ib., vol. vii, 1912. 



(5) " On Branchiura Sowerbyi Beddard, and on a new species of Limnodrilus with distinctive 



characters," Trans. Roy. Soc, Edin., vol. xlviii, pt. ii, 1912. 



EXPLANATION OF PLATE. 



All figures drawn by the help of Zeiss's Abbe drawing apparatus, and with magnification 190. The 

 great swelling of the genital region in the sexual animal is obvious. 



Reference Letters. 



An., anus ; at., atrium ; e.g., cerebral ganglion ; chl., chloragogen granules ; chl. 1 , those in the prostomium ; 

 chl. u , those behind the cerebral ganglion and over the interior end of the pharynx ; chl} 11 , those around the 

 posterior end of the pharynx; clit., cells of the clitellum ; cm., circular muscle fibres; d., duct of sper- 

 matheca ; d.v., dorsal vessel ; e.p., unmodified epithelium between the male pores ; lip, lip of everted 

 intestinal epithelium at the anus; l.m., longitudinal muscle fibres; in., indifferent cells in the region of 

 growth; p., parasite in sperm-sac; p.c, peritoneal cells; ph., pharynx; ph. d., dorsal diverticulum of 

 pharynx; ph. gl., gland cells on pharynx; or., oesophagus; sp. s., wall of sperm-sac; splh., spermatheca ; 

 Spa., spermatozoa (the heads are represented by the black lines ; the non-staining tails, not individually visible, 

 are represented by the shading on the dorsal side of the heads) ; t., testis ; v. def., vas deferens ; v.n.c, 

 ventral nerve cord ; v.v., ventral vessel. 



Fig. 1. Hxmonais laurentii; longitudinal section through anterior end, rather to one side of the 

 middle line. 



Fig. 2. The same; transverse section through middle of pharyngeal region. The dorsal and ventral 

 sides are distinguished by the dorsal vessel and ventral nerve cord respectively ; the distortion of shape is 

 probably due to the specimen having been examined under a coverslip in cedar oil before being sectioned. 



Fig. 3. The same ; longitudinal section through hinder end. The shaded mass ventral to the gut is a 

 thick aggregation of indifferent cells, here not individually represented, from which new segments are 

 being produced. 



Fig. 4. The same ; transverse section through the seminal funnels. 



Fig. 5. The same ; tranverse section through the region of the atria. 



Fig. 6. The same ; transverse section through the spermatheca?. The spermathecal pores are at the 

 anterior limit of the clitellum ; owing to the specimen having been slightly curved dorsoventrally, it was 

 impossible to get accurately transverse sections throughout the series ; the present one being slightly oblique 

 shows the clitellum dorsal to the situation of the pores, but not ventrally. 



TRANS. ROY. SOC. EDIN, VOL. L, PART IV (NO 20). 108 



