TRANSACTIONS OF THE SECTIONS. 77 



On the Cause of the Variation in the Eggs of British Birds. 

 By 0. GEOOM-NAriEK. 



On tJie Crustacea, Echinodermata, Polyzoa, and Coelenterata of the Hebrides, 

 By the Rev. A. Merle Noeman. 



On the Structure and Groivth of the Ovai-ian Ovum in the Gasterosteus 

 Leiurus. By Dr. W. H. Ransojt. 

 The author described the mode of growth of the early ovarian ovum, and drew 

 attention to the contents of the germinal vesicle, which he showed to be gela- 

 tinous ; to the germinal spots, which he showed to be drops of a thick fluid, apt to 

 imdergo singular changes of form, somewhat resembling those met -ndth in pus cor- 

 puscles ; and to the yelk sac, which he showed was present at a very early stage 

 of the formation of the egg ; and he endeavoured to prove that it increased in all 

 dimensions by interstitial deposition. 



On the Systematic Position of the Pronghorn (Antilocapra amerlcana). 

 By P. L. ScLATEE, M.A., Ph. B., F.R.S. 



The author stated that his chief object in the present communication was to 

 bring into more pi'ominent notice a very important discovery regarding this animal, 

 that had been made in the Zoological Society's Gardens in the Regent's Park 

 during the past year, and had formed the subject of a paper read by Mr. Bartlett, 

 the Superintendent of the Gardens, at one of the Society's meetings in 1865*. 

 This discovery was, that the horns of the Pronghorn were naturally shed every year — a 

 phenomenon hitherto quite unknown among the Bovidfe or hollow-horned Rumi- 

 nants, with which the Pronghorn had always hitherto been associated, and only 

 occurring in the allied Deer-family or Cervidae. Mr. Bartlett's observations had 

 been made upon a young male of this scarce mammal, which had been acquired 

 for the Society in January 1865t, and had since lived in good health in the Mena- 

 gerie. This animal had shed both its horns on the 7th of November, 1865 ; and a finer 

 pair had since otowu, which woidd, no doubt, be shed in like manner in Nov. 1866, 

 bince Mr. Bartlett's publication of this novel fact, full confirmation of it had been 

 received by the Zoological Society, in a communication from their CoiTcsponding 

 Member, Dr. Colbert A. Canfield, of Monterey, California, who had come to the 

 same conclusion as Mr. Bartlett, from observations on this animal in a state of 

 nature made in the county of Monterey, in some parts of which the Pronghorn was 

 very common |. 



The author exhibited a skull of the Pronghorn with the horns fully developed 

 and ready to be cast oft' shortly, and explained the mode in which he supposed the 

 shedding to be effected. After the old horn was cast off, the horny matter, which 

 was at first entirely confined to the upper end of the new horn, gi-adually spread 

 itself down to its base, enveloping the numerous hairs with which the new horn 

 was clothed when first appearing, and ultimately checking their growth and 

 destroying their vitality. After the horn was perfected and hardened, new hairs 

 developed themselves beneath the epidermis, and, not being able to force their way 

 through the horny covering, became, as the author believed, the chief agent in 

 causing the shedding of the horn. As regards the general structure of the horns of 

 the Pronghorn, it was quite evident that they had little or nothing in common with 

 those of the Deer. The latter were formed of bone developed upon a process of the 

 frontal bone, and were more correctly termed antlers, whereas the horn of the Prong- 

 horn consisted of true horn (like those of the ordinary Bovidfe) gradually developed 

 from the epidermis, the skin remaining complete underneath them. 



Two other points in which the Pronghorn differed from all the other known 



* "Remarks upon the AfRnities of the Prongbuck," by A. D. Bartlett, Superintendent 

 of the Society's Gardens. (Proc. Zool. Soc. 1865, p. 718.) 



t See notice and figure, Proc. Zool. Soc. 1865, p. 60, pi, 3. 



J See Dr. Canfield's paper " On the Habits of the Prongbuck, and the periodical 

 shedding of its horns," Proc. Zool. Soc. 1866, p. 105. 



