TOL. LIII.] PHILOSOPHICAL TRANSACTIONS. 43 



arch, or disposed into a straight line, according to the motion of the trunk. The 

 fins likewise are composed of 2 skins: the outer one strong and leathery, and 

 covered over with an infinite number of crimson streaks, the inner skin is thin 

 and clear: the cylindrical part of the suckers are in the same manner, only with 

 this difference, their outer skins may be softer. Both the fins and suckers are 

 hollow, so that the cavity of the suckers may communicate with the fins, as their 

 cavity does with the trunk. 



" We now come to the appearance which this animal makes when alive in sea 

 water. The trunk then was contracted circularly at the bottom of the naked 

 part of the stem, and by this contraction formed a zone of the most intense 

 purple, which moved upwards and downwards successively: when it moved up- 

 wards through the length of the pinnated trunk, it there became paler, and at 

 length terminated at the top: the motion being scarcely finished, a like zone ap- 

 peared at the end of the naked trunk, which finished its motion in the same 

 manner as the former. When this zone becomes very much constricted on every 

 side, the trunk above it swells and acquires the form of an onion; and then it 

 appears as if a compressed globe moved along through the whole space of the 

 trunk; this constriction of the trunk gives that fine red colour to the zone; for 

 when the skin of the trunk is outwardly full of purple papillae, the intermediate 

 spaces are of a whitish colour. In this constriction then of the skin, the inter- 

 mediate spaces are obliterated, and the papillae are brought nearer together; 

 consequently only the purple colour presents itself to the eyes and appears more 

 bright. 



" The end or apex of the naked trunk is sometimes curved like a hook, and 

 sometimes extended in a right line; both these motions then must be directed by 

 the little bone in the inside, and from this motion of this little internal bone, that 

 sinus or cavity at the lower end of the trunk (thought by authors heretofore to 

 be the mouth) seems plainly to be formed; for sometimes it is deeper, sometimes 

 shallower; it is deeper while the moveable globe appears in the middle of the 

 pinnated part of the trunk, and shallower when it is in the bottom of the naked 

 trunk, at which time the bone is most extended. The fins or pinnulce have 4 

 different motions; they are moved both towards the naked stem, and towards 

 the pinnated stem; sometimes they are drawn in very much to the belly, a little 

 after they are inclined to the back; further, the fleshy filaments or claws move 

 in all directions, and the cylindrical part with the filaments is either extended out 

 or drawn in and hid in the fins." 



In the following 3 chapters Dr. Bohadsch describes 3 other kinds of sea pens. 

 One he calls penna grisea or the grey sea pen with crenated fins; this is figured 

 and described from a dry specimen in Seba's Museum, torn. 3. The next is a 

 very singular one, without fins, having a square bony stem 2 feet 10 inches long, 



G 2 . . ' 



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