136 Messrs. W. K. Brooks and G. Lefevre on 



appears to me to be further in accord with the fact that this 

 tissue has, in the allied forms, lost all organogenetic power, 

 this having passed entirely to the internal vesicle. The 

 accumulation of vitelline reserve in the cells of this wall would 

 be a new step in this modification of the ectodermic layer in 

 the phylogenic series of blastogenesis. 



3. This variability in the bud, lastly, recalls, without 

 being identical, the phenomena classed by Giard under the 

 name paecilogony. 



XIX. — Budding in Perophora. By W. K. BrOOKS 

 and George Lefevre *. 



(Abstract of a paper presented to the National Academy of Sciences, 

 April 2.3rd, 1896.) 



In the 'Johns Hopkins University Circulars,' no. 119, 

 June 1895 t> the junior author of this paper published a short 

 note on the budding of Perophora viridis, Verrill. From a 

 further and more exhaustive study of the subject we have 

 since arrived at fuller and more detailed results than those 

 obtained at that time, and now give in brief a summary of 

 the chief points in the budding of this Ascidian, in anticipation 

 of the complete paper, which will appear shortly. 



The material which has been at our disposal was obtained 

 at Beaufort, N. C, and at Woods Holl, Mass., and contained 

 an unlimited supply of buds. The results are based on a 

 study of an uninterrupted series of stages of both serial sec- 

 tions and buds mounted as total preparations. 



The buds are formed in a single row on one side of the 

 branching stolons, and always arise in the plane of the stolonic 

 double-walled partition, which divides the cavity of the stolon 

 longitudinally into two compartments or sinuses. The latter 

 contain the free cells of the blood and are in open communi- 

 cation at all times with the body-cavities of the buds, so that 

 a free circulation of blood is kept up from the one to the 

 other. 



The definitive median sagittal plane of the bud coincides 

 with the plane of the stolonic partition, and therefore the 

 latter structure divides the stolon into a right and left half in 

 reference to the parts of the bud. 



* From the ' Johns Hopkins University Circulars ' for June 1896, 

 pp. 79-81. 



+ Reprinted in the ' Annals ' for 1895, vol. xvi. p. 213. 



