1884.]- Zoblogy. 731 
= _ 3. Segmentation, which is, exceptionally among Annelids, per- 
fectly regular. eae 
4. Formation of gastrula by a typical invagination. 
5. The early appearance of a preoral band of cilia and its sub- 
sequent disappearance and replacement by a row of longer, more 
cilia. 
6. The transformation of the gastrula into a trochosphere by a 
peculiar method of growth. 
7. Origin of mesoderm as two-fold, and the segmentation of 
mesodermal bands. 
8. Origin of ventral nerve chord from the ectoderm as a bilat- 
structure. 
ANaToMY OF THE STOMACH OF STALK-EYED Crustacea.—This 
Subject, lately treated by E. Nauck, is being discussed in a more 
extended manner by F. Mocquard in the Annales des Sciences 
Naturelles. As is well known the stomach of the Decapoda is 
armed at the pyloric end with numerous calcareous pieces which 
Project into the cavity and constitute, in the author’s opinion, a 
powerful apparatus for the trituration of the food, while the mem- 
branous invaginations give rise to a more or less complicated val- 
vular system, Nauck, who published his paper in the Zeitschrift i 
Tir wissen. Zoologie, described the gastric skeleton alone of the 
crabs, but Mocquard extends his investigations to all the stalk- 
eyed Crustacea, and also studies the muscles and stomachic 
serves, The figures already published appear to have benr cae: 
fully and clearly drawn. Meanwhile, F. Albert has an illustrated 
article on the same subject in the Zeitschrift fiir wissen. Zoologie, 
Published Dec. 21, 1883. 
THE Cravrisn Not DimorpHous.—It has long been supposed 
Saale Species of Cambarus were dimorphous, there being two 
abdominal appendages. But in a paper published in the American 
Journal] 
He received a lot of living Cambarus rusticus from Kentucky, males 
tig “first form” and females, which bred freely in confinement. 
ar pairing, three of the males moulted. These soft-shelled in- 
the “first form |” After attaining the “ first form” and after pair- 
, the same individual has reverted to the “second form. It - 
N clear that we are not dealing with a case of true dimorphism, 
as is well known among insects and plants, but it 27 
in the “4 that the two forms of the crayfish are alternating periods 
a tle of the indivi ‘ 
| the Pairing season, the “second form” during the intervals between 
