No. 2.] DEVELOPMENT OF PETROMVZOIV. 263 



missure (Fig. 8, PI. VIII. This drawing is erroneous in so far 

 that the commissure is not shown, and a histological difference 

 is indicated between the right and left ganglion, which does not 

 exist). For some time the left ganglion persists in this condi- 

 tion without essential change. Its later increase in size is at first 

 in the antero-posterior direction, accompanying the epiphysis 

 in its forward growth, but not extending quite so far forwards 

 as the pineal vesicle. In larvae, between the lengths of 12 and 

 25 mm., a great change takes place. As Ahlborn has shown, 

 the left ganglion habenulae has by this time become distinctly 

 divided into two parts, of which the anterior is in close contact 

 with the lower vesicle of the epiphysis (see his Fig. 43). In 

 the adult, these two portions become quite widely separated, 

 the anterior one accompanying the growth of the pineal vesicle, 

 and partially coalescing with the lower division of that vesicle; 

 a fibrous tract connects the two divisions, and, at first sight, 

 appears to be a portion of the pineal stalk. These changes 

 apparently take place at the time of metamorphosis, as I have 

 not detected them even in advanced Ammoccetes. The poste- 

 rior division of the left ganglion retains its relative position in 

 the adult; it is comparatively small, and does not, like the 

 right, project above the level of the brain and form a conspic- 

 uous object from without. 



The Pituitary Body may be conveniently described in con- 

 nection with this region of the brain. In my former paper I 

 stated that the hypophysis was derived from the nasal involu- 

 tion. Gdtte has very justly claimed this discovery as his own 

 (16), and complained that I did not acknowledge the priority 

 due to him. This was done for two reasons: (i.) The subject 

 was barely touched upon in my first paper, which dealt only 

 with the embryonic as distinguished from the larval develop- 

 ment, while the complete history of the pituitary body, includ- 

 ing a discussion of Gotte's statements and theoretical views, 

 was reserved for my second paper, which was at that time nearly 

 ready, and was expected to appear immediately. (2.) From 

 the letter which Gotte very courteously wrote me, and the 

 sketches which accompanied that letter, I inferred that he had 

 mistaken the process of development of the body in question, 

 the original statement in the " Entwickl. d. Unke " being very 

 brief, and not very clear. But in this, as appears from what he 



