381 



elemente der Spicula zu deuten sind. Sie liefern die Form des zu- 

 künftigen Spiculum und scheiden dann in sich die Kalksuhstanz ab, 

 in der erst noch die Kerne zu erkennen sind, die aber schließlich das 

 Ganze so erfüllt, daß von der organischen Grundlage nichts mehr zu 

 sehen ist und das Gebilde homogen und glänzend erscheint. Diese 

 Umbildung vollzieht sich im Mesoderm. 

 Neapel, am 5. Juli 1891. 



3. The Lateral Eyes 1 of Spiders. 



By Kamakichi Kishinouye, Science College, Imperial University, Tokyo, Japan. 



eingeg. 10. Juli 1891. 



In order to compare Limulus and the spider with respect to the 

 development of their eyes, I re-examined my sections of spiders and 

 found that I had overlooked a very important stage in the development 

 of the lateral eyes of spiders in my recent paper 2 , so that my views on 

 this point were in part incorrect. This obliges me to write briefly 

 about the new conclusion I have arrived at. 



All the lateral eyes of spiders, generally three pairs, arise from a 

 common thickening of the hypodermis on each side at the posterior, 

 external corner of the lateral vesicle when it is not yet completely cut 

 off from the general ectoderm — at about the stage of the reversion of 

 the embryo. The thickening is 

 slightly invaginated and con- 

 sists of cells arranged in many 

 irregular rows (Fig. 1 ) • 



After the process of the re- 

 version of the embryo has greatly 

 advanced, the invagination dis- 

 appears and the hypodermic thi- 

 ckening is now flat above the la- 

 teral vesicle, which is at this time 

 separated from the general ecto- 

 derm. 



When the reversion of the 

 embryo is almost over, a differen- 

 tiation occurs among the nuclei 

 of the hypodermic thickening. 

 At three places in the thickening, 

 nuclei become a little larger and 



Fig. 2. 



dorsal 



ventral 



ventral 



Fig. 1. Longitudinal sections through the 



»optic area« of the lateral eyes. Fig. 2 shews 



only the »anterior lateral eye« and the 



»posterior lateral eye«. Zeiß. 2 D. 



1 »Nehenaugen« of B e r tka u. Arch. f. Mikr. Anat. 1886. 



2 On the Development of Araneina. Journal of ScienceCollege, Japan, vol. IV. 1890- 



24** 



