204 



angesehen weiden können. Denn beide unterscheiden sich neben der 

 Färbung, auf die gar kein Gewicht gelegt werden darf, bloß durch 

 die »conspicuously emarginate« resp. »truncate with the corners roun- 

 ded caudal tin.« cf. Heckel, 1. c. p. 70 und 77, Fußnote). Ich 

 besitze übrigens einige beinahe und einen völlig sc h up pen losen 

 Nemachilus barbatulus Günth. aus unseren Teichen. 

 Schlau pitz, Dom., Kr. Keichenbach, Schlesien, 11. Mai 1891. 



5. A Preliminary Note on the Development ot Limulus longispinus. 



By K. Kishinouye, Imperial University, Tokyo, Japan. 



eingeg. 23. Mai. 



The following is a brief recapitulation of the results of the investi- 

 gations which I carried on in the Zoological Laboratory of Imperial 

 University, Tokyo, Japan on the embryology of Limulus longispinus. 

 A more detailed accotmt of them will be published in the Journal of 

 the College of Science, Imperial University, Japan. 



1) Germinal Layers. — About 9 days after fertilization, a blasto- 

 dermic thickening comparable to the »primary thickening« of the 

 spider l may be seen on the ventral surface of the egg. The thicken- 

 ing gradually extends and afterwards becomes an ellipsoidal disc. The 

 indifferent cells of the thickening separate into 2 layers — ectoderm 

 and mesoderm, and form the rudiment of the ventral plate. 



About 14 days after fertilization, the mesoderm is divided into 

 many transverse metameres and almost simultaneously into two lateral 

 parts, beginning at the anterior end. About 4 days later we find at the 

 posterior end of the ventral plate a little median groove from which 

 mesodermic cells proliferate. This groove probably corresponds to the 

 »secondary thickening« of the spider. 



The endoderm is represented by the yolk cells , which remain in 

 the interior of the egg. This process may be considered as an abbre- 

 viation of a process found in some other Arthropods, in which all of 

 the segmentation nuclei come at one time to the surface of the egg, 

 and afterwards some of them return to the yolk and form the endo- 

 derm. 



2 Segments and Appendages. — At first the segments of the 

 cephalic lobe and the 1 st appendage is cut off from the anterior end 

 of the ventral plate as one segment. Then posterior to this segment, 

 the segment of the 2nd appendage is cut off, and in succession the 



1 Kishinouve, On the Development of Araneina , Journ. Sc. Coll. Japan. 

 vol. IV. 



