ZOOL— Vol. II.] RISEN— OLIGOCHMTA. 167 



number of known species of Di-plocardia to nine, which is 

 probably but a small fraction of what will be found in the 

 future. 



Morphological Features. 



There are several structural details in the finer anatomy 

 of Diflocardia which are of more than common interest, 

 for example, the glandular crop in somites XIV and XV, 

 which is found in at least one of the species, Diplocardia 

 Michaeheni, and which may exist in others. In another 

 species, Diplocardia JSiseni, Michaelsen found lime-secret- 

 ing tissues in the same somites. This structure is said by 

 him to resemble that of the calciferous diverticles without 

 partaking of the diverticular nature. 



Another interesting morphological feature of this genus 

 is the structure of the prostate. I have investigated the 

 prostates of D. smgularis caroliniana, D. Udei and D. 

 Michaeheni . In all these species the prostates are exteriorly 

 more or less tubular, but the surface is rough, warty, wavey 

 and uneven. Longitudinal sections show the lumen of the 

 glandular part in D. caroliniana to be rather wide and 

 straight, continuing regular from one end to the other. It 

 is lined by large columnar epithelial cells as is usual in all 

 higher terrestrial Oligochaeta except the Ocnerodrilini. 



In the glandular prostate of D. Michaeheni the lumen is 

 very narrow, being no wider than the lumen of the muscular 

 part; and instead of being unbroken it sends out along its 

 entire course numerous large or small side branches into 

 which open the glandular prostate cells, though some also 

 open in the main canal. The main lumen, as well as the 

 branches, is lined by what appears to be a membrane con- 

 sisting of thin, narrow strands of connective tissue, in which 

 no nuclei are seen. In other words, the inner epethelial 

 layer of cells, which is supposed to be characteristic of the 

 higher Terricolse, is wanting. 



In D. Udei the main lumen of the glandular prostate is 

 so irregular and branching that none of the sections show 



(6) December 20, 1899. 



