REARING OF SERPULID LARV.K. 309 



were furnished without at the same time heating the water to 

 such an extent as to kill the larvae themselves. 



Under the above treatment the larvae flourished and success- 

 fully went through the transformation from the free-swimming to 

 the sedentary condition. They settled down on the sides of the 

 vessels in great numbers about fourteen days after fertilization 

 and observations could readily be made upon them with a hori- 

 zontal microscope. The examination of the larvae can undoubt- 

 edly be facilitated by the suspension of glass slides in the water 

 at the places where the free-swimming larvae are about to attach 

 themselves. The slides with the attached larvae can then be 

 transferred to shallow dishes of sea water and examined with the 

 microscope in its ordinary upright position. 



A study of the development of the opercula in the serpulids 

 constituted my main object in rearing the larvae and a description 

 of this feature is incorporated in a paper now in press. 1 A few 

 incidental observations on the behavior of the young animals are 

 given in the following notes : 



BEHAVIOR OF THE YOUNG SERPULIDS. 2 



Tlic Free Swimming Larvtz. - - As soon as the pre-oral band 

 of cilia is well developed the young larvae swim toward the sur- 

 face of the water and collect there in great numbers, especially at 

 the edges near the glass sides of the jar. They are always more 

 crowded in certain regions than in others, but the exact relation 

 of this crowding to a phototactic response was not made out be- 

 cause of the complex relations due to refraction and reflection of 

 the light within the jar. The greatest crowding was usually on 

 the side of the jar facing the window and on the side directly 

 away from the window. At the latter place the collection of 

 larvae may have been due to a secondary reflection of the light 

 within the jar. 3 



^'Compensatory Regulation." To appear in the Journal of Experimental 

 Zoology, Vol. II., No. I. 



2 Hydroides dianthus (at Cold Spring Harbor), unless otherwise noted. 



3 A. Giard ('76) in his " Note sur 1'embryogenie de la Salmacina Dysteri Huxl." 

 ( Compt. Rend., Tome 82, 1876, pp. 233-235, 285-288) says that the free-swimming 

 larvre of Salmacina collect on the sides of the aquarium facing the light while they 

 settle down and form tubes on the side away from the light. 



