694 MR. F. K. BEDDARD ON NEW [DcC. 20, 



of the aquatic OligochaBta and of Moniligaster is to be seen in the 

 genus Eudrilus. But Moniligaster obviously comes much closer to 

 the aquatic Oligochaeta than does Eudrilus in this particular. 



Communicating with this muscular penis is the atrium. I have 

 already described and figured the structure of the atrium in Monili- 

 gaster barwelli, and have pointed out its close similarity to the 

 atrium of the Lumbriculidse ; the Tubificid Branchiura has an 

 atrium which is also constructed upon the same plan. In MoniU- 

 (jaster hahamensis we have the same low and darkly staining 

 columnar epitlielium lining the lumen ; this is surrounded also by 

 the same comparatively thick circular muscular layer; in M. haha- 

 mensis, as in M. barwelli, the outermost covering of the atrium is 

 formed by oval groups of pear-shaped cells. I find, however, that 

 in the species of Moniligaster with which the present paper deals, 

 the ducts of these cells, which are simply filiform prolongations of 

 their substance, pierce the muscular layer in bundles and evidently 

 pour their secretion into the Inmen of the atrium. These ducts 

 were exceedingly conspicuous owing to their dark staining, an effect 

 possibly due to the presence of abundant secreted granules. They 

 were probably overlooked in Moniligaster barwelli, owing to their 

 not being stained. I could find no peritoneal layer even of the 

 tbinnest round the atrium. 



Rosa has described a somewhat different structure for the 

 " prostates " (atria) of Desmogaster. He has above all insisted upon 

 the presence of a peritoneal layer investing the organ superficially. 

 The minute structure is described in the following words : — 

 " II lume interno e piccolissimo, appena -^ del diametro ; esso e 

 tappezzato da un epitelio cilindrico. Esternamente a questo la 

 massa delle pareti e prevalentemente muscolare ; nella parte piu 

 centrale le fibre sono annulari ; in tutto il resto sono longitudinali, 

 disposte in fasci raggianti. Nella regione piu esterna questi fasci 

 divergendo racchiudono fra di loro delle ghiandole pluricellulari 

 piriformi che per lunghi condotti vanuo a raggiungere il lume 

 interno, ma queste ghiandole uon arrivano alia parete esterna deila 

 prostata perche i fasci muscolari, beuche ridotti a sottili strischie, 

 passano fra una ghiandola e 1' alta e si ricongiuugono fra loro, formando 

 spesso solo un sottile rivestiniento attoruo alia base di esse. E inoltre 

 ben evidente un rivestimento esterno peritoneale che spesso nelle 

 sezioni si vede staccato. La superficie delle prostate non e racemosa 

 como nei 3Ioniligaster, ma liscia o apptna ondulata, ed ha lo stesso 

 aspetto sericeo delle prostate degli Eudrilus." This description and 

 the illustrative figure are suggestive rather of the penis than the 

 atrium of Moniligaster, particularly with regard to the gland-cells 

 imbedded among the muscles. It appears to me to be possible that 

 Desmogaster differs from Moniligaster in that the atrium is not 

 specialized into two regions. 



The ovaries are in the xith segment, attached to the front wall 

 of that segment, as is so usual ; the oviducal funnels open opposite 

 to them and appear to be particularly large ; but the most remark- 

 able feature of the female reproductive organs of this Annelid are 



