376 Miscellaneous. 
Nevertheless I am struck with this cireumstance, that the rugose 
Corals, with a tetrameral type, are hardly ever found, except in the 
transition-rocks ; they therefore preceded the secondary Corals of the 
hexameral type, just as in the embryos of our living Actiniz we see 
appear 4 and then 6 tentacles. The history of the organisms on 
the surface of the earth consequently resembles the development of 
an existing animal. 
Some species of the Actinize seem to be reproduced with the 
greatest facility by means of little fragments abandoned by the foot. 
I have ascertained this process of multiplication in all the indi- 
viduals of Sagartia pellucida* that I kept in captivity in 1872 and 
1874. Dicquemare discovered the strange fact in Metridiwm dian- 
thus. 
Spontaneous scissiparity is, on the contrary, the most common 
mode of propagation in Sagartia ignea. 1 have observed it also in 
Anemonia sulcatat. It never takes place in Sagartia effeta, and in 
many other species which I have examined. The tendency to scissi- 
parity and to reproduction by means of the fragments of the foot 
would have nearly the value of a specific character.—Comptes 
Rendus, November 23, 1874, p. 1207. 
Action of Light on the Development of the Young of Frogs. 
M. Thury took the eggs of Rana temporaria and placed them all 
under precisely the same favourable circumstances, except that while 
part received light through colourless glass, another part received 
it through green glass. The former developed rapidly, and by the 
end of May had a length of four centimetres, and well developed 
hind legs in most of them; while the latter were slowly developed, 
blackish in colour, hardly had a length of two centimetres by the end 
of May, and were without a trace of the hind legs. By the 10th of 
June the former had their fore legs and some were changed to frogs; 
the latter, still black, had no trace of legs, and breathed almost ex- 
clusively by means of their gills. By the 15th of July all the 
former had become frogs; but those of the latter still had no legs, 
and by the 2nd of August they were all dead without a trace of legs 
having appeared. Some of the young of the latter lot, transferred to 
the vessel of the former on the 15th of July, finished their metamor- 
phosis. At the same time some of the former transferred to the 
vessel containing the latter continued to develop, showing the in- 
fluence of the first impulse in their development.—L’Jnstitut, Dec. 23, 
1874. 
* On the 23rd of August, 1872, a Sagartia pellucida abandoned about 
ten fragments of the foot; on the 25th of August they became rounded ; 
on the 5th of September one of them bore 8 tentacles; on the 7th of 
September the same fragment presented 15 or 16 tentacles. 
‘ On the 18th of September, 1874, an Anemonia sulcata divided spon- 
taneously, brought together its divided integuments; on the 21st of 
September the new-formed disk spread out, and the rudiments of the new 
tentacles were seen; on the 28th of September there were 20 tentacles. 
