66 DRS. CARPENTER AND CLAPARRDE ON TOMOPTERIS ONISCIFORMIS. 



necessary that any special provision should be here made for the aeration of the nutritive 

 fluid ; and we accordingly find neither branchiye nor any trace of what is commonly 

 described as the sanguiferous system in Annelida. The centres of the nervous system 

 would seem to consist solely of the cephalic ganglia, — the absence of the ordinary longi- 

 tudinal series being apparently related to the very incomplete segmentation of the body, 

 and constituting a link of affinity to the Tm-bellarian Worms. The ocelli present a con- 

 dition of extreme simplicity ; yet the duplication of the corneule in each of them marks 

 that tendency to repetition which so peculiarly distinguishes the Articulate type. It is, 

 however, the extreme simplicity of its generative apparatus, that constitutes one of the 

 chief points of interest in the organization of Tomopte^ns. It is clear that both ova and 

 spermatozoa are first developed within those prolongations of the general cavity of the 

 body which support the pinnulse, — the " germ-cells" being certainly, and the " sperm-cells" 

 probably, contained in the substance of their walls. The ova being speedily set free, 

 escape into the general cavity of the body, no proper ovaritxm being formed ; but the 

 spermatozoa remain enclosed within a sac, which is probably formed by an extension of 

 the inner layer of the wall of the perivisceral cavity, and thus constitutes a definite testis. 

 It seems clear that the ciliated canal or " segmental organ " has here only a secondary 

 relation (if any) to the genital apparatus. It has no other character in the ovigerous 

 appendages, than it has in the lateral appendages generally ; and if in the spermigerous 

 appendages the contents of the testis escape through its minor orifice, they do so without 

 traversing the principal canal. Whether the spermatozoa, Avhen diffused through the 

 surrounding water, normally pass into the ciliated canals of the female, and thus make 

 their way to the ova contained in the perivisceral cavity, or whether their entrance (as 

 seen by us) was merely accidental, like that of any other minute particles that might be 

 drawn in by the ciliary current, is a point to be determined by further inquiry. 



To the notices we have already given of the accounts of Tomopteris recorded by pre- 

 vious observers, we have to add that this creature long since presented itself to that inde- 

 fatigable student of the Marine Zoology of our coasts, the late Sir John G. Dalyell ; and 

 that it is described and figured in his work on the ' Powers of the Creator displayed in 

 the Creation' (vol. ii. p. 260, plate 36. figs. 16, 17) imder the designation of Nereis 

 phasma, or the Spectre Nereis It may be well to cite his account of the animal, for 

 the sake of his vivid description of its extraordinary transparence, and also because 

 comparatively few have access to the work in which it appeared. 



" One evening, early in January, while inspecting a vessel of sea-water, my attention 

 was attracted to an indistinct vortex amidst it, without presenting any definite object to 

 the view. This motion was connected, however, with an air-bubble, certainly shifting it 

 to different parts of the vessel. I could account for neither. Nothing else was perceptible ; 

 and it seemed still more singular that I should afterwards witness the same by day. But 

 on altering the position of the vessel so as to throw different shades of light upon it and 

 its contents, I discovered with much surprise that the agent was a very active animal, by 

 no means so diminutive as to escape detection, but of such excessive transparence as to 



