1895.] Embryology. 501 
solid aggregate and do not appear as open or half blastulæ: nor is 
there any peculiarity about the gastrula stage except its small size. 
One of the first few cells forms an irregular solid mass by cleavage ; 
one of the first four and also three of the first four cells when left alive 
also form a compact mass that does not represent a half, a quarter or 
a three-quarter individual, but a whole one. 
There is thus no semi-morula. 
The chorda dorsalis is like that of a complete egg larva and not a 
half structure. 
The author thus adds the ascidian to the echinus, frog, fish, medusze 
and siphonophores as cases in which an isolated blastomere has been 
found to produce, not a partial, but a complete individual. 
It will be remembered that Roux, in the frog, and Chabry,* in the 
ascidian; as well as Chun, in the ctenophores, find cases where an iso- 
lated blastomere does not make a complete individual but wai a half 
or a partial one. 
The results obtained by Chabry are in Driesch’s opinion the same 
as those he himself has just obtained, though otherwise interpreted by 
Chabry, Barfurth and Roux. 
Considering the differences in the methods employed by Chabry and 
Driesch we can scarcely expect a very close agreement in the results. 
Chabry carefully thrust a fine needle into one cell and left the other 
little disturbed. Driesch violently shook both cells so that one did 
not continue to live and the other, its equal, must have been much 
changed in its relation to the first cell as well as internally altered by 
the mechanical jar. 
Frogs’ Eggs in Salt Solution.—Professor Oscar Hertwig’ has 
applied the method first used by T. H. Morgan in the study of the 
frog’s egg to a more detailed examination of the abnormal results fol- 
lowing when the eggs are kept in water containing common salt. 
He finds that when eggs of Rana esculenta or R. fusca are put into 
water containing from 1 per cent to 5 per cent sodium chloride they 
develop abnormally ; in the stronger solution they are soon killed, in 
the weaker not for several days. 
Larve that develop in a 6 per cent solution of salt are abnormal 
only in the remarkable failure of the blastopore to close, as already 
noted by Morgan, and in the failure of the medullary folds to close 
over in the middle region of the brain. 
* American Naturalis., July, 1892. 
5 Archiv. f. Mik. Anat. 16 Feb., 1895. 
