22 University of California Publications in- Zoology, [^^l. 4 



Gonads. — Ovaries consisting of a single, much elongated cyl- 

 indrical mass on each side, extending from antero-dorsal to 

 postero-ventral. Testes consisting of closely crowded nodular 

 masses grouped around the posterior ends of the ovaries. 



Although this species is a typical Styela quite devoid of strik- 

 ing specific characters. I still find it impossible to assign it to 

 any hitherto described species. On the whole it seems to have 

 more in common with a Straits of Magellan form described by 

 Michaelsen, and regarded by him as a variety of S. canopus 

 (Sav.), which he names magalhaensis, than with any other 

 known form. This variety, however, usually has distinct siphons, 

 and two ovaries on each side, though according to Michaelsen, 

 1900, the siphons are occasionally wanting, and in a few instances 

 but a single ovary on each side is present. Were both these 

 variations to occur in the same specimen, the resemblance to our 

 species would be close indeed. However, it seems that the long 

 free ends of the branchial folds in S. milleri are without a coun- 

 terpart in S. canopus var. magalhaensis. Probably also the test 

 of this latter form is thicker and more uneven than it is in S. 

 milleri. 



It is interesting to note that this Styela shares with other 

 deep-sea species the trait of possessing nothing distinctive of its 

 remarkable habitat as contrasted with shallow water or even 

 littoral species of the genus. Going upon the testimony of 

 Culeolus in particular, but of other deep-sea genera as well, the 

 generalization might be reached that deep-sea life causes degen- 

 eration of the branchial membrane. The abyssal Styelas exhibit 

 no evidence of such effects. In the present species, for example, 

 the membrane is if anything rather stronger than usual. It 

 might be conjectured, I suppose, that these particular deep-sea 

 species have not been subjected to this unusual environment 

 long enough to produce the change. But what is the evidence 

 of their being new arrivals in the great depths? There are now 

 eight species, namely, batJiybia Bonnevie, bytliia Herd., flava 

 Herd., pusilla Herd., squamosa Herd., glans Herd., oblonga 

 Herd., and milleri Eitter, known from great depths, and it seems 

 as though some of them should show the beginning of reduction 

 of the sac if it is true that an effect of this sort is an inevitable 



