338 Miscellaneous. 



During the development which succeeds this stage the following 

 important changes set in : — 



(1) The anterior portion of the cerebral vesicle, which was joined 

 to the intestine, acquires an opening into the latter, and thus forms 

 a communication between intestine and cerebral vesicle which 

 persists throughout the whole of the larval period. 



(2) The multilaminate left wall of the cerebral vesicle produces 

 nearly at its middle a thickening, which gradually becomes con- 

 stricted off, and goes to form the permanent ganglion. 



The left wall itself, which hitherto formed an undivided mass in 

 conjunction with the permanent ganglion, after the latter has 

 become constricted off assumes an epithelial character. In front 

 it is directly continuous with the anterior portion of the cerebral 

 vesicle. This portion also becomes epithelial, elongates, and repre- 

 sents the well-known ciliated pit. 



(3) Now while the larval brain (formed by the evagination of 

 the right wall of the cerebral vesicle) becomes constricted off and 

 disappears, the epithelinm-like left wall of the original cerebral 

 vesicle bends round into a tube, which represents an immediate 

 prolongation of the ciliated pit just described, and in which we 

 recognize the hypophysis. 



(1) In the development of the larva, as in that of the bud, we 

 consequently find that the hypophysis and the persisting ganglion 

 have a common origin. 



(2) The common rudiment is tubular in both modes of develop- 

 ment, and in both cases the ganglion is formed as a thickening of 

 the tube. 



(3) The larval cerebral cavity opens, as described by Kowalevsky* 

 and disputed by Van Beneden and Julin t, through the hypophysis 

 into the intestine. 



(4) In the adult animals, produced from the larva, there persists 

 from the lumen of the larval cerebral vesicle only the lumen of the 

 hypophj^sis. 



The above investigations were carried out in the Zoological 

 Institute in Munich and in the Zoological Station at Naples. It is 

 a pleasing duty to express to my revered teacher. Prof. Hertwig, 

 and to Dr. Dohrn my best thanks for all the kindness shown to me. 

 — Zoologischer Anzeiger, xv. Jahrg. no. 400 (Sept, 12, 1892), 

 pp. 328-332. 



Munich, June 29, 1892. 



* " Weitere Studien iiber die Entwickluug der einfacheu Ascidien," 

 Archiv f. mikr. Anat. 7 Bd., 1871. 

 t Op. fit. 



