026 



THE AMERICAN NATURALIST [Vol. XLII 



"While Davis's work greatly weakens one of the strong supports 

 of blood relationship between these two groups, it does not leave 

 this weakening wholly uncompensated. It seems to find a 

 number of striking resemblances between the egg cleavage of 

 this particular enteropneust and that of Amphioxus. But this 

 part of the study is less full and the significance of resemblance 

 in these earlier developmental stages is more problematic. For 

 the character of the correspondences here the reader must be 

 referred to the paper itself. 



3. Ecology and Physiology. — Eitter and Davis 6 have studied 

 quite fully the movements of a tornaria of the California coast 

 from near the beginning to the end of its pelagic career. A 

 number of interesting facts pertaining to the character of the 

 swimming movements, the correlation of these with its specific 

 gravity, and this again with its structure are brought out. 



Davis (paper on the development of Dolichoglossus pusillus 

 already referred to) discusses some points on the distribution 

 and migration of this species as dependent upon the movements 

 of the animal during its larval period, and upon tidal action. 

 Davis finds that the breeding time of D. pusillus in San Diego 

 and Mission Bays is .January and February, and that the fertil- 

 ized eggs can be obtained from the burrows of the animals at 

 low tide without great difficulty. Particularly noteworthy is 

 the fact that in spite of the absence of a true tornaria, the young 

 animal still does considerable swimming, and that this follows 

 rather closely the general scheme previously found by Ritter 

 and Davis to characterize the swimming of the tornaria of 

 another species above alluded to. 



Eitter 7 has studied the movements of the adult Dolichoglossus 

 pusillus and a California species of Balanoglossus with the spe- 

 cial view of gaining a better understanding of the action of the 

 proboscis and skeletal musculatures and the relation of these to 

 the skeleton. The results make it probable that the nuchal skel- 

 eton together with the so-called notocliord serves not merely as a 

 support for the isthmus, or neck, but also as an axis upon which 

 the muscles of locomotion act, in part at least. 



4. Anatomy. — The classification of the Enteropneusta is based 

 •Studies on the Ecology, Morphology, and Speciology of the Young of 



Some Enteropneusta of Western North America. Univ. of Calif. Publica- 

 tions, Zoology, Vol. 1, 1904, pp. 171-210. 



T The Movements of the Enteropneusta and the Mechanism by which 

 they are accomplished. Biolog. Bull., Vol. HI, pp. 255-261. 



