200 SCIENCE PROGRESS. 



ever may be their functions they contain crystals of car- 

 bonate of lime, and have a rich vascular supply, the lining 

 epithelium being much folded and therefore extensive. In 

 some Eudrilidae these structures are absent or rather are so 

 altered that they are nearly unrecognisable as calciferous 

 glands. At the same time they have become more numerous. 

 The structure is altered in that instead of an extensive lumen 

 produced by the folding of an excretory epithelium there is 

 a very short sac connected with the oesophagus, which 

 is, however, enveloped by an extensive coating of cells 

 which I regard as ccelomic cells, and among which meander 

 abundant blood-vessels. These ccelomic cells, where they 

 abut upon blood-vessels, very often lose their oval or 

 rounded form and become columnar and at the same time 

 more darkly staining. They surround the blood-vessel as if 

 it were the lumen of a secreting gland, the cells themselves 

 having acquired the appearance of a secreting epithelium. 

 These phenomena suggest that we have to do here with a 

 change of function on the part of the calciferous glands ; that 

 their function of producing carbonate of lime, that their 

 connection with alimentation has disappeared or is dis- 

 appearing, and that a new function more intimately connected 

 with the vascular system has supervened. There is a 

 certain analogy here with the vertebrate liver which has 

 certainly more functions than that of pouring bile into the 

 intestine, though originally it may have been merely an 

 annex of the alimentary canal. 



In histology there is only one matter to which I shall 

 direct the attention of the reader. It concerns the minute 

 structure of muscular fibres in the Oligochoeta. The careful 

 researches of Cerfontaine have established the fact that the 

 Oligochseta, like the leeches, have muscular fibres which 

 consist of an outer sheath often radiately striated, the 

 muscular substance, and a soft central core. Hesse, how- 

 ever, while admitting this, goes a step further and 

 endeavours to prove a resemblance to the muscular fibres 

 of the Nematoidea. He figures in the Enchytraeidae and 

 in the Lumbricidse a gap in the sheath of the fibre through 

 which the soft less-modified protoplasm of the interior com- 



