PART II. 



ANATOMY AND PHYSIOLOGY OF HALICLYSTUS AURICULA. 



CHAPTER IV. 

 GENERAL FORM AND STRUCTURE. 



§ 6. Hahitaf, Ilahits, Form, and She. 



29. Form and Proportions (PI. i figs. 1-17). — In some of the attitudes {fuj. 1) 

 of this species, the form of the body, as a wlioh^, might be compared to a lady's 

 parasolette heavily tasselled at eight about equally distant points around the edge. 

 Tlie handle, then, would correspond to the thick, short peduncle at the caudal end 

 of the body, and the ferrule-bearing tip would rejjresent the proboscis. Imaghie 

 the parasolette turned inside out so that the usually concave under side becomes 

 convex, and it would then have the shape which our Lucernarian most frequently 

 assumes {fi<j>^. i-T). It might, then, also be sometimes compared {fig. 5) to a 

 broad, shallow, eight-sided fruit dish supported by a pedicel. 



30. Size. — Keeping up the simile to the parasolette, or umbella, we proceed to 

 indicate the size and proportions of this umbelliform mass. Full-grown specimens 

 measure one inch {figs. 2, 3) across the umbel, or sometimes a little more, especially 

 those collected at the latter end of the breeding season in our more northen, colder 

 seasons. Including the tassellated tentacles the wiiole is equal to one and a half 

 inches from side to side. The peduncular, caudal portion is at least one-half an 

 inch long, and about one-twelfth of an inch thick, on the average, but, expanding 

 rather abruptly at the extreme posterior end, into a truncate, discoidal, adherent 

 termination, it is there a little more than one-eighth of an inch. The proboscis is 

 the least conspicuous subdivision of the body, on account of its position and trans- 

 parency; and, as it is extremely sensitive to the touch and highly contractile and 

 extensible, its proportions can be made out only approximately, and therefore we 

 can but say, in general terms, that it is about one-eighth, or from one-eighth to one- 

 sixth of an inch long, or from one-fourth to one-third the length of the peduncle, 

 and about as broad, in the average, as long. From these measurements, one would 

 judge that the animal before us is, on the whole, rather stout and heavy in its 

 proportions ; certainly it is not slender, nor even approximately so, although it has 

 a pretty wide range of general extensibility, and in some of its attitudes appears to be 

 considerably elongated {fig. 7), but in the latter case this is more seeming than real. 



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