242 ARTHUR WILLEY. 



primary association with the neuropore, the notochord inter- 

 vening. I knew this had happened in the case of the mouth, 

 my views on this point being acceptable to MM. Delage and 

 Herouard, but I had not, until recently, realised that a 

 similar change had affected the prseoral pit. 



It will therefore be seen that Legros has probably touched 

 upon the fringe of a fundamental truth, so far as the mor- 

 phology of the prseoral pit is concerned, although led thereto 

 by erroneous premises ; moreover the same truth was broached 

 by Bateson, to whose work the author makes no reference. 



The contradictory result as to the origin of the prseoral pit 

 arrived at by Legros would, if true, very seriously discredit the 

 work of Hatschek, but it has nevertheless been well received, 

 Klaatsch/ for example, ingenuously and uncritically rejoicing 

 at the '' Correctur der Hatschek'schen Angabe ;" and it has 

 been adopted by MM. Delage and Herouard. 



Hatschek's discovery of the conversion of the left head-cavity 

 into the prseoral pit, which has been confirmed, let it be re- 

 peated, by MacBride, was a matter of unbiassed observation, 

 and must have come as a serious shock to his sense of coelomic 

 propriety. To contradict Hatschek on this point in ignorance 

 of the living transparent embryos, and to base the contradic- 

 tion entirely upon sections through material preserved in sub- 

 limate and acetic, is surely very rash. The Belgian author 

 has obviously, in this matter, been a victim of the microtome, 

 but it is to be feared that his results will more or less dominate 

 the subject throughout the next decade, since they have already 

 found a home in a leading treatise. 



The external orifice of the club-shaped gland is a minute 

 pore below the anterior end of the larval mouth ; it is invari- 

 ably to be seen in all living larvae before the metamorphosis, 

 but is not always easy to find in transverse section. Of course 

 Legros does not find it, and he denies its existence.^ 



1 Hermann Klaatscb, " Ueber den Bau und die Entwickelung des Tenta- 

 kelapparates des Amphioxus," 'Verb. Anat. Ges. (Auat. Anz.),' 1898, 

 p. 184. 



* See also E. Ray Lankester and A. Willey, " Tbe Development of tbe 



