442 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 45. 



Reproductive system. — On both sides, consisting of intermingled 

 lobes — not numerous — of ovary and testes; most of the left gonad 

 situated within and in front of the intestinal loop. 



The species is undoubtedly closely akin to Eugyrioides arctica Bon- 

 nevie, 1896; in fact, resembles it so closely that I have hesitated 

 about making a separate species. However, as the descriptions of 

 arctica now stand, the two differ in the following particulars: dalli 

 grows to a considerably larger size than arctica. The latter is 

 devoid of the surface filaments that are characteristic of dalli. The 

 branchial tentacles of arctica are described by Bonnevie as being 

 "lobed like an oak leaf." As my figure 2 shows, this is quite 

 different from the tentacles of dalli. Finally the wide separation 

 of the two geographically makes a presumption against their specific 

 identity. 



The specimens of E. rara (which see) were mingled with those of 

 dalli in one of the bottles from Kyska Harbor, and a complete separa- 

 tion of the two mthout dissection of every one is somewhat doubtful. 

 The superficial characters on which I have relied in sorting them are 

 the more prominent and wartlike siphons, somewhat farther apart, 

 of E. dalli. But since the differences here are neither great nor 

 entirely constant, it is not impossible that more dissections would 

 find that my sorting is not altogether accurate. As the evidence 

 now stands E. dalli reaches a much larger size than does rara. This 

 criterion, I suspect, will hold, but too much reliance should not be 

 placed upon it till more evidence is at hand. The particular internal 

 differences between these two species are the larger number of lon- 

 gitudinal vessels or membranes in dalli; the larger, more numerous 

 and more highly branched tentacles of dalli; and the second order, or 

 ''free" infundibula of the branchial sac of dalli. These infundibula 

 are a very striking feature of the inner surface of the respiratory 

 membrane. The}^ are of different sizes, are irregularly distributed, 

 and make the impression, when seen under a low magnification, of 

 foreign bodies of some sort clinging to the membrane. 



Special mention should be made of the hundred and more small, 

 excessively sand-covered individuals contained in one of the Kyska 

 Harbor lots, I assume them to be the young of dalli. For one thing, 

 the siphons, though recognizable on surface views of most of the indi- 

 viduals by their light color, are far less prominent either in color or in 

 size than in the larger specimens. But differences in stage of devel- 

 opment may well account for the difference. The siphons are also 

 on the whole relatively farther apart in the smaller than in the larger 

 individuals. This, however, is by no means invariably true, so I 

 can not consider the peculiarity to be of great significance for classi- 

 ficatory purposes. In internal structure the tentacles of the small 

 animals seem to be simpler, the secondary branches being wholly or 

 almost wholly wanting. But this again may well be a juvenile 



