No. 2.] THE HYPOPHYSIS OF AM I A CALVA. 75 



I find several lumina which apparently do not communicate. 

 Neither do my observations agree with those of Balfour and 

 Parker on Lepidosteus at a corresponding age, where the 

 hypophysis is described as " small, not divided into lobes, and 

 provided with a very small lumen"; whereas in Amia at this 

 period it is much lobed and possesses numerous spherical 

 lumina. 



Kupffer (loc. cit. p. 59) has described a very early and unusual 

 formation of the hypophysis in Acipcnscr sturio. According to 

 him the organ arises during the second clay after fertilization 

 by an invagination of the basal layer of the ectoderm on the 

 dorsal side of the head, in front of the brain, between the yet 

 unclosed neuropore and the sucking disc. This invagination 

 grows downwards and backwards until it comes in contact with 

 the endoderm, and then, before the close of the second day 

 (forty-five hours), by a rupture of this layer, it communicates 

 with the alimentary canal, which communication persists for 

 about twenty-four hours. But before the stomodaeum has 

 formed a connection with the foregut, this union of the 

 hypophysis with the latter has broken off (i.e., by the sixty- 

 fourth hour), and the lower blind end of the tube becomes 

 swollen into a hollow bulb. This bulb gradually enlarges and 

 migrates backwards to a position between the dorsal wall of 

 the gut and the base of the thalamencephalon, while the 

 remaining part of the tube, namely, the stalk, gradually atro- 

 phies and has wholly disappeared by the time the embryo is 

 hatched (eighty-seven hours). 



Haller has expressed a doubt as to Kupffer's interpretations. 

 This doubt is based upon the indistinctness of the parts observed 

 at this early time. From Kupffer's own words it would seem 

 that the cells were greatly obscured by food-yolk. I give the 

 passage quoted by Haller : " Die Entodermzellen sind noch 

 mit Dotter uberladen, die Zellen der Epidermis und des Hirnes 

 schon fast dotterfrei, aber diejenigen Ektodermzellen, die in 

 der Bildung der gleich zu besprechenden Organe (Hypophy- 

 scnanlage, etc., Haller) eingehen, zeigen noch denselben Dotter- 

 vorrath wie die Elemente des Entoderms und sind daher durch 

 Farbungen von diesen nicht zu unterscheiden. Die Abgren- 



