IIO W. J. CROZIER. 



the pigmentation of A. atra seems to me indicated by the finding 

 of well-grown and densely black specimens in small caves prac- 

 tically shut off from the light. A few such were discovered with 

 the aid of an electric torch in cavelets having but a small opening 

 to the water. And from the under surface of a submerged rock, 

 undercut in such a manner as to be completely sheltered from the 

 sun, I later secured a group of fair-sized individuals with a quite 

 normally black appearance. 



5. Summary. Pale, translucent individuals of the blue-black 

 Ascidia atra, a species normally occurring in sunlit places, are 

 found in darkened situations under stones. They resemble, in 

 the absence of test-pigment, ascidians of other species habitually 

 living in shaded spots. In spite of the fact that such pale A. 

 atra may quickly blacken if placed in sunlight, it is pointed out 

 that the absence of natural pigmentation cannot be regarded as 

 due to darkness, but is probably a consequence of faulty nutrition. 



CITATIONS. 

 Caullery, M. 



'95 Contributions a 1'etude des ascidies composees. Bull. Sci. Fr. Belg., Tom. 



27, pp. 1-158. 

 Crozier, W. J. 



'16 Some Indicators from Animal Tissues. Jour. Biol. Chem., Vol. 24, pp. 



443-445. 



'20 Behavior of a Tunicate Larva. Anat. Rec., Vol. 17, p. 344. 

 Day, E. C. 



'19 The Physiology of the Nervous System of the Tunicate. I. The Relation 

 of the Nerve Ganglion to Sensory Responses. Jour. Exp. Zool., Vol. 28, 



PP- 307-335- 

 Fuchs, H. M. 



'14 The Effect of Abundant Food on the Growth of Young Ciona intestinalis. 



Biol. Centralbl., Bd. 34, pp. 429-434. 

 Goldfarb, A. J. 



'10 Light as a Factor in the Regeneration of Hydroids. Jour. Exp. Zool., 



Vol. 8, pp. 133-142. 

 Grave, C. 



'20 Amaroucium pellucidum (Leidy) form constellatum (Verrill). I. Jour. 



Exp. Zool., Vol. 30, pp. 239-257. 

 Hecht, S. 



'iga The Physiology of Ascidia atra Lesueur. I. General Physiology. Jour. 



Exp. Zool., Vol. 25, pp. 229-259. 



'i8b ... II. Sensory Physiology. Ibid., pp. 261-299. 



'i8c . . . III. The Blood System. Amer. Jour, Physiol., Vol. 45, pp. 157-187. 

 'i8d The Photic Sensitivity of Ciona intestinalis. Jour. Gen. Physiol., Vol. i, 

 pp. 147-166. 



