. Carnegie Institution di Washington la pubblicazione. 106 carte del laboratorio biologico marino a Tortugas. I primi cinque delle prove di cui sopra sono stati effettuati 2 ore dopo il funzionamento e il saldo di circa 24 ore più tardi. Il metodo di manipolazione e l'orientamento sono stati variati, ma vi è ogni indicazione che la stella di mare ha reagito positivamente verso il vivacemente illuminate fine del piatto. In ogni test ma 2 dei 18, il echinaster spostato verso la luce estremità. Il secondo giorno dopo il funzionamento il comportamento era più diretto. Non vi può essere alcun dubbio che l'occhio-spot come pure io centimetro del

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. Carnegie Institution of Washington publication. 106 Papers from the Marine Biological Laboratory at Tortugas. The first five of the above tests were made 2 hours after the operation and the balance about 24 hours later. The method of handling and the orientation were varied, but there is every indication that the starfish reacted positively toward the brightly lighted end of the dish. In every test but 2 of the 18, the echinaster moved to the light end. On the second day after the operation the behavior was more direct. There can be no doubt that the eye-spots as well as i centimeter of the ray are not neces- rary in the reaction of Echinaster crassispina to the light. The rest of the surface of the starfish must be sensitive to light (Jennings's work indicates this) to such a degree that the direction of movement is influ- enced by it. In fact, since this work was done I have tested the sensitive- ness of the tube feet and the gills of Pentaceros reticulatus and have found that they react definitely to changes in intensity of light. Besides the series of tests recorded in table 8, other series equally convincing were undertaken with different individuals; furthermore, we shall see in some later experiments additional proof that an echinaster without eye-spots is sensitive to light; while there is no doubt that eye- spots are not necessary, yet it is true that echinasters with these organs removed do not react as quickly as normal individuals. Whether this is the result of the injured condition or the lack of the eye-spots I can not say. DIFFERENCE IN INTENSITY OF ILLUMINATION AND RAY DIRECTION AS FACTORS IN DETERMINING THE DIRECTION OF LOCOMOTION. So far as I know, Jennings (1907) has been the first to attempt to ascertain whether the direction of the rays of light or the differences in the intensity of illumination on the different parts of the body determine the direction of locomotion of the starfish. By manipulating a screen in various ways, so as to cut out

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• bookauthorcarnegie
• bookcentury1900
• bookdecade1910
• bookyear1911