ON THE STHUCTUKE OF 7F.NIGMA J^lNlGJiATIGA. 271 



into the right wall of the kidney sac nearly opposite to, but 

 a little further back than, the reno-pericardial funnel. So 

 far the only difference between the structure and position of 

 these organs in Enigma, and those in Anomi a, as described 

 by Sassi, consists in the fact that whereas that author says 

 there are no ciliated funnels to the gonaducts in the latter 

 genus, there are very distinct gonaducal funnels, with a 

 well differentiated ciliated columnar epithelium (tig. 15) in 

 /Enigma. 



In respect of the relations of the reno-pericardial funnels 

 to the remnants of the pericardium, there is, however, a 

 great difference between the two genera. Sassi has shown 

 that in Anomia ephippium the reno-pericardial canals 

 lead into a system of short and slightly branched tubules 

 ending in glandular diverticula, and these he identifies, no 

 doubt correctly, as the remnants of the pericardium. I have 

 already shown that Enigma is in several respects a less 

 specialised form than Anomia, and in this particular matter 

 of the reno-pericardial ducts and their connections it has 

 clearly undergone less modification than the latter genus. 

 Fig. 14 is a drawing of a section through the left reno- 

 pericardial canal of Enigma. The canal is lined by a 

 columnar epithelium, each of whose constituent cells bears a 

 long flagellum. The upper end of the canal is lined by a 

 Hatter non-ciliated epithelium, and passes into a mass of 

 reticulate glandular tissue containiug many inter-cellular 

 spaces. Though it is not particularly well shown in the 

 section figured, the communication between these spaces 

 and the reno-pericardial canal can be easily traced in the 

 series of sections. Some few sections further back the canal 

 appears to open, by an aperture so distinct that it might 

 almost be described as a ciliated funnel, into a central lumen 

 in the mass of glandular tissue, and this as it is traced back- 

 wards breaks up into a number of irregular branches or 

 channels communicating with the spaces in question. From 

 its relation to the reno-pericardial canal there can be no 

 doubt that this lumen together with the irregular channels 



