460 — . General Notes. [ May, 
ENTOMOLOGY. 
Í 
DEVELOPMENT OF THE MoLE CRICKET.—A. Korotneff has pub- 
lished in the Zeitschrift für wissen. Zoologie, XLI, 4, 570, a well 
! illustrated essay on the embryology of the mole cricket, which 
as been also noticed by C. Emery in the Biologisches Central- 
blatt for Jan. 15, in connection with Grassi’s observations on the 
i development of the honey bee. The egg of the mole cricket 
has an abundant yolk, while that of the bee has little yolk and is 
small and transparent. Yet both observers have independently 
arrived at the same results in four important points. It is note- 
worthy that in both forms before the formation of the blastoderm 
a stage was observed in which ‚the amceboid embryonal cells 
seemed to possess no clear nuclei. With this result might 
connected the relation briefly described by A. Sommer in the case 
of a Podurid, when the ripe egg was entirely without a nucleus. 
Whether there was in all these cases a genuine absence of the 
: nucleus, or a diffuse nucleus form, such as Graber discovered in 
ae the Protozoa, is still to be determined, and would not be without 
interest in connection with the late reflections of Weismann and 
. others on heredity. 
? In Gryllotalpa the embryonic cells are at first scattered over 
the surface of the egg; some migrating into the deeper parts of 
the yolk and forming the yolk cells regarded by Korotneff as the 
primary mesoderm. From the ectoderm exclusively separates 
the endoderm. There first originate, under the ectoderm cells 
which Korotneff denotes as mesenchym, and not till later does 
the separation of the myoblasts follow along the ventral median 
oe line. Later still arise from the ectoderm near the trachee other 
= — groups of cells which are also to be considered as mesenchym, 
o and which were also observed in Bombyx by Tichomiroff. 
mbryonal membranes serosa and amnion arise as ecto- 
dermal folds. After the limbs are indicated the er oat oy 
: öt 
(Tichomiroff observed the same number in Bombyx. ihe ™ 
vous system primarily shows a corresponding organization $ 
_ seventeen pairs of ganglia, which are reduced to thirteen by the 
=~ consolidation of the three hinder head-ganglia (in the text t ey 
< are erroneously called thoracic ganglia) and the three last abdom 
inal ganglia. The cerebral ganglia are first separated from €a? 
other and only joined to the ventral chain by slender commis” 
sures. The structure called “chorda” by Nusbaum is a media 
ectodermal one, which grows in between the two series of ganglia, 
and has nothing at all to do with the formation of the connective 
_ tissue of the nervous system. This last tissue must arise 
_ the immigrating blood-cells. d 
_ Especially interesting are the observations on the structure 
