ON TUBIFEX. 



149 



medium through which respiration is effected ; how far this function 

 is shared by the corpusculated fluid, or how far nutrition is also a 

 part of the function of the red fluid, are questions to which no 

 decisive reply has yet been offered, though the considerations 

 above adduced would tend (perhaps erroneously) to the conclusion 

 that respiration belongs to the one and nutrition to the other 

 exclusively. In speaking, then, of these two fluids, I prefer 

 adopting such names as ' red ' and ' colourless,' or ' vascular ' and 

 ' perivisceral ' fluids, to using the terms ' pseudohsemal ' or ' chy- 

 laqueous.' " * 



A (qw words may here be said about the integument. Gegen- 

 baur, in speaking of the integument of the Vermes, says : — " The 

 proper integument is formed, as a rule, of a layer of cefls, the 

 elements of which are often so slightly separated that they form a 

 syncitium. f This layer corresponds to an epidermis, which in 

 the Annelida is covered by a homogeneous cuticle, which varies 

 greatly in character, and is a product of the secretion of the 

 epidermic cells." This seems, so far as the descriptive portion of 

 it is concerned, to be a correct description of the integument of 

 the Limicolous Oligoch^ta, which I have examined ; but the use 

 of the terms epidermis and cuticle, so far as they may imply 

 homologies, is a point on which some confusion, if not difference 

 of opinion, would appear to exist, and which I should like to point 

 out, even if I cannot settle. D'Udekem, as I have already stated, 

 describes the integument as consisting of a delicate epidermis, and 

 of a chorion intimately united to the muscular layer. Now, from his 

 further description, it is evident that the epidermis of D'Udekem 

 is the homogeneous cuticle of Gegenbaur and his chorion 

 (corium ?) the cellular epidermis of the latter. The same reversal 

 of the term epidermis appears in Lankester's description of the 

 integument of the Earthworm, t where ^ epidermis ' is again applied 

 to the external structureless layer ; the cellular layer beneath it, 



* The Anatomy of the Earthworm, by E. Ray Lankester, Journal Micr. 

 Sci., Vol. v., New Series, page lOO. 



t A syncitium is that condition of living matter wherein nuclei are 

 scattered in a mass of protoplasm without the protoplasm itself being marked 

 off into separate cells corresponding to the nuclei. 



t The Anatomy of the Earthworm, by E. Ray Lankester, Journal :\Iicr. 

 Sci., New Series, Vol. IV., p. 260. 



M 



