1918.] G. S. Thapae ; The Lym'ph Glands in Pheretima. 71 



THE GLANDS AS SEEN IN DISSECTION. 



Pheretima hawayana. — The lympli glands are a double series of whit- 

 ish bodies, situated on either side of the dorsal vessel, lobulated, segment- 

 ally arranged, beginning in segm. xxvi. In the anterior portion of 

 their extent they occupy the posterior third of each segment, and extend 

 from the dorsal vessel outwards about half way towards the lateral 

 margin of the intestine. As we pass backwards they enlarge, until in 

 the middle region they cover the greater part oi the intestine in each 

 segment (fig. I). Still further back they diminish again, and ultimately 

 they totally disappear in the last two or three segments. Each consists 

 of a large number of very closely set small lobules. 



The septa are pouched forwards where they cross the dorsal vessel 

 so that the dorsal vessel is here enclosed in a tube-like sheath, the cavity 

 of which is part of the cavity of the segment behind the septum. It is 

 to the walls of this pouch that the glands are connected. 



On some of the glands a number of small white bodies are to be seen, 

 which on examination are found to be the cysts of the spores of a Gre- 

 garine, — probably of the Moviocystis found in the seminal vesicles. 



Pheretima heterochaeta. — The glands begin in segm. xvii. In the 

 anterior part of their extent they appear attached by a short stalk ; 

 behind, the glands enlarge and a stalk is not to be distinguished ; at the 

 hinder end the glands of a pair meet and fuse over the dorsal vessel and 

 below it, so that the vessel is enclosed by the glands. The glands are of 

 simpler form than in P. hawayana, — not lobulated in the same way ; 

 though towards the hinder end a number of lobes, with a digitate arrange- 

 ment, may be present (fig. 2). 



Pheretima fosthuma. — The glands begin, as in P. hawayana, in segm. 

 xxvi ; the lobulation and variations in size correspond to what was 

 found in that species ; some of the glands also show the spore cysts of 

 Gregarines. 



HISTOLOGY OF THE GLANDS. 



A detailed description need only be given for one species ; for this 

 purpose I choose P. hawayana. 



The lobules of the gland surround a central cavity, and this cavity 

 opens into the cavity of the sheath round the dorsal vessel at this region ; 

 the interior of the gland is therefore morphologically in connection with 

 the cavity of the segment behind that in which the gland itself lies. 

 Fig. 3, actually drawn from P. fosthuma, will illustrate this relation. 



The boundary of the gland consists of an extremely fine membrane, 

 in which nuclei appear at intervals as flattened swellings ; these ovoid 

 nuclei contain a deeply staining granule (" pseudonucleolus "), as well 

 as fine irregularly distributed chromatin particles ; the protoplasm sur- 

 rounding the nucleus appears to be fibrillar in structure, and is continued 

 into the membrane which forms the boundary of the gland. 



Besides this bounding membrane, the interior of the gland is tra- 

 versed by a reticulum, sometimes comparatively sparse, of the same 

 character, — much flattened cells joined end to end, — and continuous 

 with the limiting membrane, or capsule, as it may be called. In the 

 centre of the gland this reticulum is almost or quite absent, so that there 



