MUSEUM OF COMPARATIVE ZOOLOGY. 221 



The egg of Nanomia in the eight-cell stage is the oldest which has been 

 studied. There seems to be nothing peculiar in the method of segmentation 

 as compared with that of Agalma. Among other medusae it has some like- 

 nesses with that of the Ctenophora and certain Trachymedusse. 



Between the eight-cell stage and the youngest as figured by A. Agassiz 

 there is a considerable gap, which I am not able to fiU by new observations. 

 This interval is, however, in part bridged by observations on an allied genus 

 found in the Mediterranean, already published by Metschnikoflf. This ob- 

 server * has studied a Siphonophore, which is closely allied to Nanomia, and 

 seems to resemble in mode of growth, as far as known, that which has been 

 already described and figured by A. Agassiz. 



Older larvae, which he supposes to belong to the same genus, Metschnikoflf 

 has raised from planulae which are a little younger than the youngest Nano- 

 mia figured by A. Agassiz. He has shown that in these larvae no " primitive 

 hydrophyllium " t is formed, and that the first structure to develop is the 

 float. He regards his genus as the same as Nanomia. 



A few years ago I was inclined to regard the genus referred to by Metschni- 

 koft* as the same as Nanomia. The adult tentacular knobs described for the 

 first time m- this paper confirm me in that opinion, but there is one thing 

 which leads me to doubt their identity. The existence of the large oil glob- 

 ules in the bases of the tasters is very exceptional among Physophores. I 

 have studied the animal, Stephanomia pictum, referred to by Metschnikoff, 

 and was one of the first to describe it,t but I do not remember seemg struc- 

 tures similar to the " oil globules " of the tasters of Nanomia. In the 

 published descriptions of this animal there are no similar structures. The 

 question then arises whether the presence of this structure is sufiicient to sep- 



* Op. cit. 



t The term "primitive hydrophyllium" was suggested in my paper on the 

 development of Agalma to designate the cap-shaped covering scale which forms 

 such an important organ in determining the form of the larva. The designation 

 " primitive larva," used to distinguish the stage in which this organ is most de- 

 veloped, was suggested in the same paper. The primitive larva is supposed to 

 be an ancestral form of Calycophores and Physophores, and to be closely allied 

 to the ancestral form of other Hydromedusae. 



X Contributions to a Knowledge of the Tubular Jelly-fishes, Bull. Mus. Comp. 

 Zool., Vol. VI. No. 7, pp. 136, 137, Plate II. Neither in Metschnikofrs figure of 

 Stephanomia, nor in Claus's figure of Hnlistemma tergestinum, which all seem to re- 

 gard the same, the relative size of the hydrophyllia seems to be smaller than in 

 Nanomia. The same is true of my Agalmopsis from Florida. Claus's figure of the 

 taster of his Halistemma, Plate II. Fig. 4, shows what maj- be a small " oil glob- 

 ule" near the base of this organ, and the structure in the same figure lettered mg, 

 "male sexual bell," has some resemblance to the "oil globule" of Nanomia. 

 Still from his description it does not seem that tiie " oil globule " has the predom- 

 inance in size which it has in Nanomia. It must also be said that \i mg (Plate II. 

 Fig. 4) is a male sexual bell, it is very different from the same bodies in Nanomia. 



