The Cambridge natural history . on its head for some time, as ifinvestigating the nature of the rocks on which it may settle: itis extremely contractile, turning its head from time to time,anil seldom retaining the same outline for any length of time ; thesetae are protruded, and at times stick out in every direction;they are possibly defensive in function. When fully stretchedout the larva is about -^ nnn. long, but it frequently shortens itsVOL. Ill 2 I 482 RECENT BRACHIOPODA chap. body to two-thirds of this length. The larvae are of a pinkishred coloiu, with eye-spots of ruby red. Their col
The Cambridge natural history . on its head for some time, as ifinvestigating the nature of the rocks on which it may settle: itis extremely contractile, turning its head from time to time,anil seldom retaining the same outline for any length of time ; thesetae are protruded, and at times stick out in every direction;they are possibly defensive in function. When fully stretchedout the larva is about -^ nnn. long, but it frequently shortens itsVOL. Ill 2 I 482 RECENT BRACHIOPODA chap. body to two-thirds of this length. The larvae are of a pinkishred coloiu, with eye-spots of ruby red. Their colour rendersthem diflicult to discern when they are swinnning over the redcoralline rocks upon which they frequently settle. After swim-ming about for a few hours the larva fixes itself finally,apparently adhering by some secretion produced by the stalksegment. The folds of the second or body segment then turnforward over the head, and now form the ventral and dorsalmantle folds; these at once begin to secrete the shell on their. Fig. 320.—Stages in the development of the larva of Terehratulina septentrionalis. (AfterMorse.) The youngest larva has two segments, a third then appears, the larvathen fixes itself, and the second segment folds over the first and develops bristlesround its edge. outer surfaces. The head with its eye-spots must l)e to someextent absorbed, but what goes on within the mantle is notaccurately known. The setae drop oif and the tentacular armsbegin to appear as a thickening on the dorsal lobe of the are at first circular in outline. The various changes whichthe larva passes through are well illustrated Ijy Morse for Tere-hratulina, which spawns at Eastport, Me., from April till different stages are represented in outline in Fig. 320, takenfrom his paper. Habits There is little to be said about the habits and natural historyof the Brachiopoda. When once the larva has settled down, theanimal never moves from the spot selected; occasio
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
