MUSEUM OF COMPARATIVE ZOOLOGY. 141 



by Mr. Alex. Agassiz and Kowalevsky. He says : '* Die Aelteste von 

 Kowalevsky gezogene Larve mit Luft apparat Magen und Fang faden 

 gleicht so sehr dem juugsten von Alex. Agassiz gefangenen Jugendzu- 

 stande der Nanomia, dass es mir sehr wahrscheinlich ist, dass auch diese 

 Physophoride in die Gattung Stephanoraia eingezogen werden muss zumal 

 zwischen beiden eine grosse anatomische Analogie besteht." The absence 

 of the cap-shaped provisional bell in the very young Nanomia shows 

 that it does not belong to the genus Agalma, and the fact that a float 

 and not a nectocalyx is first developed, separates it from Ualistemma. 

 Metschnikoff''s conclusion seems to me the most natural one. I there- 

 fore would refer it to the genus Agalmopsis, of which I regard Stepha- 

 nomia, as ordinarily used, a synonym. 



There are certain points in which, following the description by Mr. 

 Alex. Agassiz (North American Acalephae, pp. 200 - 213), Nanomia differs 

 from the other related Siphonophorse which I have studied. He says 

 that the float in this genus contained a globule of oil. I have never 

 seen the genus fully grown in our waters, and can only judge from my 

 studies of most of the other genera of the justness of Metschnikofl"s 

 criticism (Studien der Medusen und Siphonophoren, p. 36) of Alex. 

 Agassiz on this point. If the float does contain oil, I think it an excep- 

 tional case among Siphonophores. 



The second kind of feeding polyps, as described in Nanomia, are, I 

 believe, simply immature forms of the first, and the tightly-coiled cork- 

 screw parts are only undeveloped tentacular knobs. I have often found 

 the young knobs of Agalma Sarsii and A. elegans clustered in the same 

 manner at the base of a feeding polyp before a true tentacle had been 

 formed. 



The resemblance of the tentacular knob of Nanomia, with its " cnido- 

 fils," as shown in Mr. Agassiz's drawing (Fig. 339), to the provisional 

 structures bearing the same name in Agalmopsis picta and the " Athory- 

 bia stage " of Agalma, is very great. This likeness is a very interesting 

 fact, indicating either an embryonic condition of the adult of Nanomia, or 

 that it is the larval form, sexually mature, of another Siphonophore. 



The origin and earlier development of Nanomia cava, according to Mr. 

 Agassiz, as a bud from the stem, is, I think, exceptional. In those other 

 Siphonophores whose development is more or less completely know^n 

 through the studies of Glaus, Haeckel, Kowalevsky, and Metschnikoff*, 

 we find only an egg development of the new colony. 



Dana describes (Mem. Amer. Acad., Vol. II. Part I.) a Physophorid 

 from the Pacific Ocean. He calls it Crystallomia j)olygonata. The 



