STUDIES ON THE PROTOCHORDATA. 327 



that the Ascidians are more closely related than Appendicularia 

 to these protochordata. 



'' The features upon which he lays most emphasis are these : — 

 I. The endostyle is at first vertical and pre-oral ; II. The organ 

 of fixation is a pre-oral lobe, and its cavity is the pre-oral or 

 anterior body-cavity j and III. The first four primary stigmata 

 of Ciona intestinalis are developed from one primitive gill- 

 slit 



" I cannot believe that students of the Tunicata will regard 

 the first and second of these arguments as entitled to the least 

 consideration." After this very decided expression of opinion. 

 Professor Brooks goes on to say, " It has long been known 

 that the endostyle of Ascidian larvae is at first vertical or at 

 right angles to the long axis, and it is so figured and described 

 by Seeliger ; but the relative position of organs is so much 

 influenced by changes in other organs that we cannot attribute 

 a phylogenetic significance to the position of the endostyle." 

 It was certainly so described and figured by Seeliger for 

 Clavelina, and as a tribute to the excellence of his description 

 I quoted a considerable portion of it verbatim in my paper 

 (loc. cit., pp. 331, 333). 



The point on which I insisted, however, was that in the larva 

 of Ciona, a simple Ascidian whose development in comparison 

 with that of Clavelina is remarkably uncompressed, the endo- 

 style behaved in the way stated by me, and not as described 

 and figured by Kowalevsky in the case of a closely allied 

 simple Ascidian. It is not a light thing to impeach Kow- 

 alevsky^s accuracy, and I considered it important to call 

 attention to the actual relations of the endostyle in the larva of 

 the simple Ascidians, which had not been done before. 



With regard to the second half of the above-quoted para- 

 graph, I will merely point out that the primary position of the 

 endostyle in the larva is that which it holds prior to the 

 changes in the arrangement of the other organs, in which it is 

 subsequently involved. 



The method by which the endostyle attains its secondary 

 and final position has nothing whatever to do with the question 



