134 
POPULAE SCIENCE EEYIEW. 
body, whilst the drawing power of a horse is only *67 of his weight. As the 
result of 500 experiments on different insects, he states generally that the 
power exerted is inversely proportional to the weight of the insect. This 
interesting paper was ordered to be printed in the Bulletin. 
Historic Age of the Bog. — M. Quatrefages has presented to the Academy a 
curious memoir on the origin of the race of dogs. In China, he states, the 
exact period of the introduction of the dog is well known. It was in the 
year B.C. 1122, that is about 3,000 years ago, or about the period of the 
siege of Troy. The dog appears, from what the writer asserts, to be a domes- 
ticated jackal, and the jackal a savage dog. 
Do Male or Female Moths first emerge from the Pupa ? — This query is 
replied to by Mr. E. Birchall, of Bradford, who concludes that a few females 
are the first to appear ; that about the middle of the flight the numbers of 
sexes are equalized, and that the males continue to appear for a day or two 
after all the females have emerged from the pupa ; and this appears to be 
an arrangement admirably calculated to provide a partner for every female. 
From various causes female moths appear to be less numerous than males, 
but he believes this to be only in appearance : the female has more im- 
portant business in hand than sipping sugar, or flying round a lamp, and is 
also more lethargic in her habits. He has been struck with the equal 
division of the sexes in broods reared from the egg ; for instance, in the 
large brood of L. caniola reared this year, the number of each sex is exactly 
the same ; whereas at large he has never captured more than one female for 
ten males of this species. 
The Zoological Society’s Gardens. — In the list of the vertebrated animals,, 
published recently, the distinguished editor, Dr. Sclater, gives the subjoined 
table, which is quite sufficient to show the prosperous condition of the 
association, and its efforts to promote the interests of science : — 
January 1st. 
1855. 
1856. 
1857. 
1858. 
1859. 
1860. 
1861. 
i 1862. 
1863. 
1864. 
Quadrupeds. 
387 
394 
443 
379 
285 
364 
467 
450 
485 
567 
Birds 
768 
770 
802 
775 
881 
819 
931 
843 
1114 
1063 
Reptiles . . . 
104 
118 
156 
137 
156 
137 
192 
121 
149 
10O 
Total ' 
125 
1282 
1401 
1291 
1322 
1320 
1590 
1414 
1748 
1730 
The Microscopic Anatomy of the Hydrozoa. — Professor Kolliker has pub- 
lished his researches upon the histology of the hydrozoa, in the Natural 
History Journal of Wurzburg. In these animals he distinguishes three- 
kinds of connective tissue. Gne forms the tentacles of the hy droid polyps, 
and all the solid tentacles of the Medusae. It presents the appearance of a 
series of cells {muscular cells of Keferstein) occupying the axis of the ten- 
tacle. These cells possess no contractility ; at least, the tentacles of the 
uEginidse and Trachynemidse which present this structure are rigid. The- 
contractile tentacles owe their contractility to a muscular layer situated 
between the cellular axis and the external epithelium. This cellular axis is 
only a dependence of the internal epithelium which lines the digestive cavity 
(Hydroids), or the marginal canal, (Medusa?). It probably acts as an elastic- 
