ACALEPH 2. Lt7 
1. 1804, p. 134, Pl. vi fig. 3, A, B,C. The two pieces provided with 
swimming cavities, nearly similar in form, were afterwards, by 
Cuvier (Régne Anim. sec. éd. 111 p. 288) and other writers, 
erroneously taken to be two animals which had become attached 
to each other, an opinion occasioned by observing that they 
were readily separated. This separation, or spontaneous detach- 
ment of different parts, has often been remarked in the entire 
order—as in Physsophora, Rhizophysa, Stephanomia. In fact, 
Diphyes is much more nearly allied to these genera than might 
be suspected from many, and sometimes very confused, descriptions 
of it. I may remark, that the part which, in our description, 
we have indicated as anterior, is called posterior by the first 
discoverer, Bory, and by many others after him. 
Quoy and Gaimarp, who discovered many new species of this 
family and formed new genera from them, (Ann. des Se. nat. 
Tom. x. 1827, p. 5—21,) determined subsequently to bring them 
all under the single genus Diphyes, (Voyage de découvertes de 
? Astrolabe, Zoolog. Tom. tv. 1833, p. 81). [But more accurate 
observations of late years have shewn that this proceeding is not 
advisable. In Praya the swimming bells are similar in form, 
and are placed, more or less, side by side, and their cavities 
open on opposite sides of the stem. In Diphyes the bells are 
placed behind one another and open backwards. 
The common stem begins within the substance of the anterior 
bell, or piece, in a more expanded portion, which is lined with 
large epithelial cells, and has very different form in different genera. 
This expanded portion often contains a globule of oily matter. 
Beneath it the stem gives origin to the canals of the swimming 
pieces, and then is prolonged to become the common axis of the 
colony. 
The polyps with their different appendages are fixed to the stem 
at regular intervals. Those nearest to the swimming pieces are 
quite undeveloped and without appendages. Those at the other 
extremity of the stem are the oldest and most perfect, and have 
their appendages most complete. Each group consists of a Polyp, 
a set of prehensile organs, and the generative organ, which partakes 
more or less of the medusan form—the whole being covered by 
a protecting bract. Such a group either persists in adhering to the 
common stem, (Diphyes, Praya), and then only certain parts are 
detached, as the medusiform capsules of the sexual organs ; or it is 
