SEAL-EMBRYOS. 21 



ILLUSTRATIONS OF LEPTONYCHOTES WEDDELLI. 



!M,AT!-; I. 



fir,, i. Dissection (if u uterus, showing the youngest fu'tus in Uic collection i,i Kiln. The hind limb is 



as long and well-developed as the fore limb. 

 F I( ; _> A. slightly older specimen, showing the position of the vestige of the external ear (*>). 



Enlarged. 



Fro. 3. The Lend of the same specimen still more enlarged. 

 FIGS. 4, 5, G, and 7. Four embryos (natural size), showing the gradual alteration in the position of the 



limbs. 

 FIG. 8. Foot of the largest embryo, showing the webbing of the digits and position of the nails. 



Natural size. 

 FIGS. 9, 10, .and 11. Three stages in the development of the liver, b. <1. = Bile duct. Natural sizes. 



Seen from ventral side. 



PLATE II. 



FIG. 12. Mesial section of an embryo, showing curvature of the cervical spine. Natural size. 

 FIG. 13. Section through the head of the oldest embryo, slightly to the right of the mesial plane. The 

 median nasal septum has been partially removed. A probe () is shown passing through 

 the external nares into the lateral nasal cavity (J. n. c.). Another (b) through the opening 

 from that cavity into the median chamber (m. <.), and a third probe (c) from that chamber 

 through the rima glottidis into the trachea (/.), which has been opened. Reduced. 



Fn;. 14. Section through the head before removal of the median nasal cartilage (. n. ntrt.}. i. r. = 

 median chamber. The lateral wall of the larynx has been removed to. show the 

 communication between the median chamber and trachea. 



FIG. 15. Dissection of the larynx from above, showing the intra-narial position of the epiglottis (rjti,//.}. 

 r. = true rima, which is r/rtiail in position; its posterior part has been drawn backwards 

 in order to expose it. r. p. = velum palati. 

 FIG. 1C. Uterine surface of the placenta. 

 FIG. 17. Section through the younger stage of the placenta. 

 a = lacuna of extravasated maternal blood. 

 b = " lamelles mcsenteriques." 



f = " angioplasmode," trophoblast, embryonic, and maternal capillaries. 

 d = maternal portion of the placenta, showing uterine glands cut across (>). 

 e = uterine glands cut across. 

 Fio. 18. Section through a slightly older placenta. 

 = mesoblast of embryo. 

 b = " angioplasmode." 

 c = maternal portion of placenta. 

 '/ = uterine glands. 





