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1894] _ Embryology. 711 
dition of seta of nephridia in the earthworm group the author’s more 
detailed future work promises to add to our knowledge of other diffi- 
cult points, such as the origin of the nerve cord, which it is here stated 
arises from two distinct matrices. 
Bourne is inclined to regard the germ bands as the source of all the 
metameric structures. The body wall muscles would be of other origin. 
The segmentation of the digestive tract a secondary state forced upon it 
by the mesoblastic structures. 
Determination of Sex.— What at first sight appears to be an 
interesting and valuable addition to the facts tending to show that favor- 
able conditions lead to the production of female offspring and unfavor- 
able conditions to the production of male offspring is to be found in a 
paper by F. Braem upon the development of a marine polychxtous 
annelid, Ophryotrocha puerilis. Here, however, as in some other cases, 
the evidence is really of little value as may be seen from the facts given 
by Korschelt in a paper immediately following that of Braem. 
Braem found in attempting some regeneration experiments in addi- 
tion to his study of the ovaries and testes that in one case there was a 
remarkable change of sex. A female annelid full of ripe eggs was cut 
into two pieces, the anterior containing 13 and the posterior 22 
segments. After three weeks the anterior part had regenerated seven 
segments. 
It had become smaller and appeared to be starving while the eggs 
had disappeared. When sectioned it was found to have changed its sex, 
containing only testes. A few cells remained that were ova in process of 
formation before the sexual glands changed their character and began 
to form sperms. 
The author would refer this transformation into a male to the un- 
favorable conditions, to the fact that the creature was not sufficiently 
nourished to form ova as well as to regenerate the lost part of its body. 
Now Korschelt in a careful study of the anatomy of this same small 
annelid finds that besides males and females, there are also herma- 
phrodites (in fact Braem found one such case) in which the same gland 
makes both ova and sperms. Among 30 individuals 6 were female, 7 
were male, 8 were apparently female but contained male cells buth 
young and full formed, white the remaining 9 were apparently male 
though containing ova in the testes. Thus the hermaphrodite state is 
the more frequent one, to judge from these few cases. 
* Zeit. f. wiss. Zool., 57. 
