296 Mr. H. M. Kyle on the Nephridia, 



the young transparent forms 3 to 4 inches in length to the 

 older and larger of 14 inches and over. It is curious to 

 notice how the external appearance of these larger forms 

 varies according to the surroundings in v/hicli they live. 

 From the clean bright gritty sand a form is got of a fine 

 golden colour, with a smooth and glossy exterior, and exuding 

 from its surface a gelatinous substance which is quite clear 

 and transparent ; from the muddy clay-flats another form is 

 procured which has a rough and coarse appearance, is of a 

 dark dirty brown colour, and gives off from its skin a green 

 slimy gelatinous material. 



From both of these forms the reproductive products may 

 be obtained, and these may either be sperm-bundles or ova. 

 The time of the appearance of these products is variously 

 given by different writers, and, judging from my own obser- 

 vations, the animals seem to spawn during a period extending 

 from January to September, though there is a cessation during 

 April, May, and the first part of June. Temperature does 

 not seem to be a determining influence, because in the height 

 of midsummer (in July) specimens with ova were obtained at 

 high-water mark, whilst in September similar specimens were 

 found at low-water mark. 



If the nephridium be dissected out from the side of the 

 body and mounted, then the drawing of it given by Benham 

 will be seen to be perfectly accurate. But this dissection 

 implies the cutting of certain tissues around — the separation 

 of the nephridium from the vascular system, the reproductive 

 organs, and the oblique muscles. In the process of mounting 

 also the nephridium is straightened out and its original form 

 thus altered. For these reasons it seemed to me right to give 

 still another drawing of the complete nephridium as seen 

 in situ. Several other drawings of the complete nephridium 

 have been given. Cosmovici's paper (3) came into my hands 

 after my own had been completed, and my drawings agree 

 with his more than with those of others. Cunningham's 

 drawing, as well as his paper (4), is far too vague and indefinite 

 to give one a proper idea of a nephridium. The drawing- 

 given by Vogt and Yung (6) agrees very closely with that of 

 Cosmovici's, but the fringes on the dorsal lip of the nephro- 

 stome are not represented. 



Ihe fringes round the dorsal lip of the nephrostomc are 

 vascular processes connected with the branchial vessel. 

 Benham describes these processes as if they were restricted 

 to the lip of the nephrostome. In reality they are continued 

 lor a short distance behind the nephrostome over the neck ; 

 this can be seen both in transverse and longitudinal sections, 



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