1901.] NATURAL SCIENCES OF PHILADELPHIA. 457 



THE NASAL PASSAGES OF THE FLORIDA ALLIGATOR. 

 BY ALBERT M. REESE, PH.D. 



The material upon which the followiog work was done was 

 received by the writer from southern Georgia, about the first of 

 August, whence it had been sent by express to Baltimore.^ It 

 consisted of about thirty eggs of Alligator mississipplensls, most of 

 which contained embryos in an advanced stage of development. 

 These embryos were fixed in Kleinberg's dilute picro -sulphuric 

 mixture, giving a fair fixation, and were stained in borax carmine 

 and Lyon's blue. Serial sections w^ere cut through the head in 

 transverse, horizontal and sagittal planes. Although the structure 

 of the nasal cavity, even of so advanced an embryo, cannot be 

 taken to represent that of the adult, there have been so few figures 

 of this character published that the following account may be of 

 interest. 



As may be seen from Plate XXIV, figs, la and 16, the embryo 

 is in an advanced state of development, and already shows distinct 

 reptilian characters. The first series of sections (figs. 2a-l) was 

 cut at right angles to the long axis of the snout of the embryo 

 (fig. lb, x-y), or rather it was intended to be an exactly trans- 

 verse series but, by faulty orientation, the sections were so cut that 

 the right side is inclined, somewhat, toward the base of the snout. 

 This departure from the exact transverse position is the cause of 

 the lack of symmetry in the two sides of the nasal cavity, as seen 

 in this series of sections. Fig. 2a represents a section through 

 the tip of the upper jaw. On the left it passes through the ex- 

 treme edge of the wall of the nasal cavity, while on the right side, 

 which is nearer the base of the snout, it cuts through the right 

 nasal aperture, r.n.a. Near the centre of the section is seen the 

 extreme tip of the nasal cartilage, n.c. The body wall, h.w., in 

 this section, as in all following sections, is represented by a heavy 

 black line. 



^American Naturalist, VoL XXXV, No. 411, pp. 193-195. 



