38 BULLETIN : MUSEUM OF COMPAEATIVE ZOOLOGY. 



the male genital pore (viii.-xr.) into somite xii., where it receives the ducts 

 of the salivary glands, a bundle from either side of the body. 



The salivary glands themselves are very large in this species and are dis- 

 tributed in the marginal part of the body through somites xi.-xvii., or, in 

 exceptional cases, even a somite farther in one direction or the other.^ 



The short oesophagus (a., Figure 13) extends from the base of the proboscis 

 through somite xiii. to the beginning of the crop in somite xiv. 



The crop (iglv., Figure 13) extends over the six somites xiv.-xix., giving 

 off in the middle of each a pair of conspicuous lateral diverticula. These are 

 always evident whether the crop contains food or not, a condition very different 

 from that which exists in G. stagualis. The last pair of crop diverticula (those 

 of somite xix.) are very long but simple, as in G. stagnalis, without secondary 

 lateral diverticula. They extend back over the entire stomach region, usually 

 ending in somite xxiii. 



The stomach (ga., Figure 13), which is separated from the crop by a valve- 

 like constriction, bears four pairs of lateral diverticula doubtless originally 

 metameric in arrangement, but now arising within the limits of somites 

 xx.-xxii. 



The intestine {in., Figure 13) leads from the stomach back to the anus, which 

 is situated dorsally just behind somite xxvii., as in other species of Glossi- 

 phonia. The intestine includes anteriorly two rather spacious chambers, the 

 first of which bears a pair of small ear-like diverticula from its anterior lateral 

 borders. Behind these chambers comes a simple tubular part terminating at 

 the anus. 



To sum up, the particulars in which the digestive tract of G. fusca differs con- 

 spicuously from that of G. stagnalis are (1) the shorter proboscis and larger 

 oesophagus ; (2) the larger salivary glands, distributed through a greater num- 

 ber of somites ; (3) the persistent character of the first five pairs of crop diver- 

 ticula; (4) the distinctly chambered condition of the intestine, and the pair of 

 diverticula borne by its first chamber. 



Nephropores are found on the sensory ring of each of the somites viii.-xxiv., 

 with the possible exception of xiii., where, as in stagnalis, the nephridia are 

 much reduced, if not wholly wanting, — a fact accounted for by the strong 

 development of the salivary glands and genital ducts in that region. The 

 nephropore lies usually a little anterior to the middle of the ring on which it 

 is found. 



e. Nervous System. 



A ventral view of the brain is shown in Figure 18, a dorsal view of that part 

 of it which lies above the pharyngeal sac is shown in Figure 16, the position 

 of the ventral part being indicated by a dotted line ; the outline of the brain 



1 The animal sliown in Figure 13 was a small one, and flic salivary-glaml cells 

 are proportionally a little larger than they would be in the average, full-grown 

 animal. 



