On the larval development of Amia calva. 667 



not SO favorably shown, have been seen by the writer in Acipenser, 

 Lepidosteus aud Amiurus, and they have also been noted in Fundulus 

 by Dr. 0. L. Strong. 



Hypophysis. 



The hypophysis is by no means as iraportant an dement in the 

 development of the head in Ämia as in the other Ganoids. Its ap- 

 pearance is late and inconspicuous. It has not been found in stages 

 earlier than that of Fig. O, and even here its presence is not definite : 

 at the most the position of its lumen can be recognized as the line, 

 HY, formed by the arrangement of cells immediately below the region 

 of the recessus opticus. These cells are apparently ectodermal for 

 they are arranged in a continuous line with the cells of the forniative 

 epiblast of the dorsal wall of the stomodeum, but on the other band 

 their ventral limit canuot be distinguished from the entodermal cells 

 roofing the foregut, FG. The tissue of the region of the hypophysis 

 in Ämia we may therefore conclude, has been brought into its defini- 

 tive Position at a relatively precocious period, and accordingly it has 

 followed that abbreviated ontogeny has siippressed many phylogenetic 

 stages. Thus the preseat writer has been unable to find that the 

 hypophysis has at any time established an outer opening or in fact 

 any fusion with the mouth roof: its wall has been entirely dififeren- 

 tiated in situ, and its slender lumen formed. Its condition in a larva 

 of one month is shown in Fig. Q at HY. The hypophysis of Ämia 

 will accordingly be seen to present well marked transitional features 

 to that of the bony fishes. 



f) Sense organs, sucking disc, ciliation. 

 The mode of development of the eye and of the nasal and olfac- 

 tory capsules dififers but little from that typical in the lower verte- 

 brates generally. As already noted by Allis the nasal capsules, in 

 their early stages, are connected with and closely correspond to the 

 neighboring sensory pits of the mucous canal System. But on the 

 other band there appears to be no evidence that the auditory sac in 

 Ämia arises as in the Teleost Serranus. Here, accordiug to 

 H. V. Wilson, a common sensory furrow is the Anlage of the ear, the 

 branchial sense organ, and the lateral line, — a condition which has 

 been generally accepted as demonstrating a close genetic affinity in 

 these associated structures. And close their affinity doubtless is, 

 although the present writer cannot regard the evidence of Serranus 



