648 E. EAT LANKESTEK. 



In referring to those researches Professor MacBride says 

 (p. 591), '' Lankester and Willey's paper on the development 

 of the atrial chamber confirms in most points Kowalevsky's 

 statements." Later (p. 605) he says^ " Kowalevsky was the 

 first to discover that the atrial cavity was formed by the 

 meeting in the mid-ventral line of two long ridges or folds." 

 And further, " Lankester terms the folds which actually wall 

 in the atrial cavity ' epipleural/ and the projecting angles 

 after these folds have united ' metapleural.' I shall use the 

 term ' atrial fold ' to include the whole, of which both are 

 parts." 



It appears to me that both in his references to Kowalevsky's 

 observations and in his iteration of the word "folds " and pro- 

 posal to call what I had called epipleur and metapleur by the 

 term " atrial fold," Professor MacBride is in error, and that 

 his statements and use of terms are inconsistent with the 

 facts demonstrated by Willey and myself. 



The region of the body of Amphioxus termed " epipleur " 

 by me (at a time when I accepted Rolph's theoretical scheme of 

 its development based on Kowalevsky's observations, and now 

 shown to be erroneous) includes the whole of the atrial wall 

 on each side from the level of the dorsal artery to the median 

 ventral raphe. It seems to me absolutely unjustifiable to 

 speak of this as a " fold " since my paper of 1890, the more so 

 inasmuch as the erroneous view of its origin (that of Rolph) 

 was that it arose as a horizontal down-growing fold. To call 

 it and the metapleur resting on it '^the atrial fold " at the 

 present day, as Professor MacBride does, is simply to ignore 

 Willey's and my results, and to perpetuate error. 



It seems that Professor MacBride has somehow forgotten 

 what Willey and I actually showed, since he declares that we 

 confirmed Kowalevsky, and further that Kowalevsky dis- 

 covered that the atrial cavity was formed by the meeting in 

 the mid-ventral line of two long folds. 



As a matter of fact, Willey and I did not confirm Kowa- 

 levsky. The whole point of our paper lay in a correction of a 

 misinterpretation made by that most distinguished observer. 



