Meyen’s Report for 1839 on Physiological Botany. 269 
development. Pagurus, Galathea, and Hyas come out in a 
less developed state, since at the time of quitting the egg they 
do not even possess a trace of legs or branchie. <Astacus ma- 
rinus, on the contrary, and Astacus fluviatilis are at that 
time already provided with all the legs and branchiz belong- 
ing to their organization. Other parts with which all Deca- 
pods appear to be then already furnished are in some at that 
time only slightly, in others, on the contrary, exceedingly far 
developed with respect to size. This relates especially to the 
antennz. On the other hand, some possess in the com- 
mencement parts which are subsequently entirely lost; as, 
for instance, in Astacus marinus appendages on the legs for 
swimming, and in Hyas Araneus a considerably long spine 
on the upper side of its dorsal shield, while in other Decapods 
such parts never occur. Or, in some, parts vanish, which in 
others are permanent, as the snout in the Paguri, and the 
lateral lamin of the fan in Hyas; and other parts again 
undergo such considerable changes in their form, that it 
becomes quite different, as, for instance, central lamina 
of the fan, the foot-jaws, and the antennz of several spe- 
cies. One of the most remarkable phenomena is, however, 
this ;—that in Decapods which inhabit the sea the members 
they employ for locomotion are in the commencement so or- 
ganized that they can solely or principally be used for swim- 
ming (as appears to be the case with the Lobster) ; in the 
freshwater Crab, on the other hand, when it leaves the egg 
those apparatus have such a structure that they can only be 
employed for walking. 
In conclusion, I would still direct attention to the circum- 
stance, that although several-Decapods, perhaps even the 
greater number of them, have in the commencement with re- 
spect to the form of their members great similarity with the 
Schizopoda, and especially with species of Mysis, yet the de- 
velopment of the two tribes of animals is very different in se- 
veral other respects. 
XX X1.—Report of the Results of Researches in Physiological 
Botany made in the year 1839. By F. J. Meyen, M.D., 
Professor of Botany in the University of Berlin. 
[Continued from p. 144.] 
From C. Sprengel, the writer on Rural Giconomy, we have re- 
ceived a work on Manures*, which is not only of high prac- 
* Die Lehre vom Diinger, oder Beschreibung aller bei der Landwirthschaft 
gebrauchlicher vegetabilischer, animalischer und mineralischer Diingerma- 
terialien, nebst Erklarung ihrer Wirkungsart, Leipzig, 1839, 8. 456 Seiten. 
