THE BIETH OF A ZEBRA HYBRID. 21 



though extremely small, are present. I am uow iu a 

 position to state that at the fifth week the second and 

 fourth digits look nearly as long and as well developed as 

 the third or middle digit, — that, in other words, the horse 

 is for a time tridactylous, the outer digits being relatively 

 nearly as large as in the adult rhinoceros. 



In addition to studying the embryos I have been ex- 

 amining the foetal appendages. The most interesting facts 

 made out in connection with these appendages are, first, 

 that the rudiments of tlie foetal villi make their appearance 

 between the sixth and seventh weeks, and are well formed 

 by the end of the eighth week ; and second, that as the 

 yolk placenta dwindles, a complex epiblastic girdle appears 

 externally, while numerous apparently non-vascular villi 

 grow out from the allantois into the coelomic space between 

 the rapidly growing allantois and the yolk-sac. 



Postscri/pt. — I find I have omitted to mention that Ro- 

 mulus is Mulatto's first foal, that his eyes are of a bluish- 

 grey colour, somewhat darker than in his sire, Matopo, 

 and that the hocks were for a time marked by narrow 

 longitudinal grooves. 



Appendix. — Measurements of Eomulus (in inches) when 

 two months old: withers to the ground, 38^; shoulder- 

 joint to the ground, 29 ; elbow to the ground, 265 ; elbow 

 to the fetlock, 20| ; cannon bone along outside, 8 ; cir- 

 cumference at knee, 8 J ; circumference below knee, 5; 

 withers on a line with anterior border of scapula to root 

 of tail, 27-J ; withers to occipital protuberance, 19; chest 

 to buttocks, 35 ; girth behind fore-legs, 39 ; length of 

 head from occipital protuberance to end of muzzle, 16i ; 

 width between eyes where narrowest, 5^; where widest, 

 9^; length of ear, 6; stifle to hock, 13; hock to ground, 

 18 ; cii'cumference of fore pasterns, 5 ; circumference of 

 hind pasterns, 51; circumference of shanks, 5^ ; circum- 

 ference of fetlock-joints, 7J ; circumference of coronets 7|. 



