MUSEUM OF COMPAKATIVE ZOOLOGY. 217 



shape is given to these bodies. The free and distal angle diagonally opposite 

 the angle of attachment is rounded and very obtuse ; the angle of attachment 

 is more acute. 



A tube extends from the point of attachment diagonally to the opposite 

 angle of the covering scale, where it ends blindly. This tube is undivided, 

 unbranched, with entire edges. 



Folypites. — The polypites (p) are flask-shaped bodies, attached by a short 

 peduncle to the polyp-stem. Their free end is open, forming a mouth. The 

 rim of this orifice, or the lips, are without appendages. The basal peduncle 

 is short, and of somewhat smaller diameter than the polypite itself. Near 

 the base the polypite bears a " Wiraperwiilst," or ferule-like thickening of 

 the walls.* At that point reddish pigment is found, and buds which are im- 

 mature tentacular knobs arise. The tentacles also originate at that point. 

 The polypites are regularly distributed along the polyp-stem, dividing the 

 stem into sections or regions, which may be known as inter-polyp regions. 

 The oral extremity of the polypite, except when it is retracted, extends be- 

 yond the hydrophyllia. The opening of the mouth sometimes expands, by 

 which the lips become trumpet-shaped. The rim of the mouth is entire. 

 Fragments of food were seen inside the polypite. Rows of large cellular 

 bodies, in parallel lines, extend along the inner wall of the polypite. These 

 are possibly hepatic in function. 



Tentacles. — The tentacles (to) are long, filamentous bodies, arising from the 

 base of the polypite. They are highly contractile, and generally, when the 

 animal is at rest, extended. Each polypite has a single tentacle. There are 

 two kinds of tentacles, one of which bears tentacular knobs, the other being 

 destitute of the same.f The former, which are the tentacles proper, are those 

 which arise from the polypites ; the latter, the filaments of the hydrocyst, 

 which have no tentacular appendages. 



The peculiar festoon-like way in which the tentacles are often carried, is 

 noticed by A. Agassiz. This habit is marked in the genus, and is more 

 common in Nanomia than in the southern genus Agalma. Although I have 

 studied all the Mediterranean species of Physophores alive, I recall none 

 where this habit is so well marked as in Nanomia. 



Tentacular Knobs. — The adult tentacular knobs (Plate II. Fig. 9) of Nano- 

 mia resemble those of Agalmopsis, Fewkes.J The various parts which enter 



* This increase in size of the polypite at the " Wimperwiilst " is largely owing 

 to the increased development of the middle layer of the body. 



t The tentacles which are destitute of tentacular knobs do not arise from 

 polypites, but from the hydrocysts. 



In the growth of the tentacles the tentacles do not first form, and then the 

 tentacular knobs bud from it, but the knobs first form on the " Wimperwiilst," and 

 then the tentacle is pushed out, bearing these bodies, already imperfectly formed. 



X One form of Agalmopsis, Sars, Stephanomia pictum, Metsch., Halistemma te.r- 

 gestinnm, Claus, Agalmcpsis fragile, Fewkes. These various aliases of Agalmopsia 

 are mentioned, lest confusion be introduced by the above statement. 



