No. 2.] STRUCTURE OF BIMASTOS PALUSTRIS. 48 1 



become very thin, but appears to never become entirely inter- 

 rupted. 



Claparede states that in Lumbricus terrestris the follicles 

 are lined with glandular cells ; in Bimastos palustris, as I have 

 shown (Figs. 9 and 10), this lining consists of a finely granular, 

 evidently protoplasmic layer, not divided into cells, and con- 

 taining numerous nuclei, many of them lying on the surface. 



I have not found the rifts, or communications, between the 

 follicles and the oesophageal lumen, which Claparede observed 

 in Lumbricus. 



Claparede's figures do not satisfactorily represent the histol- 

 ogy of this organ. 



Behind these oesophageal " pouches " the oesophagus rapidly 

 dilates to form the thin-walled, highly vascular crop. This is 

 lined by a non-ciliated nucleated epithelium of columnar cells ; 

 the outlines of the deeper portions of these cells are indistinct 

 and free(.?) nuclei are seen beneath their bases. Scattered here 

 and there are flask-shaped cells, containing a granular secretion 

 (Fig. 11,^). The epithelial cells are of irregular height, and 

 great moniliform blood-vessels still further add to the irregular- 

 ity of the inner surface. 



In the region of septum 15-16 a large valvular transverse 

 fold arises from the dorsal and lateral walls, and projects into 

 the enteric cavity. This fold is thick and vascular, and the cir- 

 cular layer of muscle being strongly developed, it forms an 

 efficient valve between crop and gizzard. In Fig. 5, which 

 purports to be a dorso-ventral, longitudinal section, this valve 

 is wrongly represented. The intestine was somewhat twisted 

 here, and the section has passed through the two lateral walls, 

 instead of the dorsal and ventral. The valvular fold does not 

 occur on the ventral wall. 



The crop occupies about one somite, XV, but a short thin 

 walled region exists in a portion of the following somite. 

 This is succeeded by a muscular gizzard, occupying somites 

 XVII and XVIII, and sometimes a portion of XVI. In struct- 

 ture, it is similar to the organ in Lumbricus, Fig. 12. 



The sacculated intestine immediately follows the gizzard, 

 and in somite XXI the typhlosole first becomes apparent. 



