AP PEIN DIX. 
Wuitr revising the index for this volume I received a note from Pro- 
fessor Thorell, calling my attention to a paper by Dr. Carl Apstein upon 
the spinning organs of spiders,! and particularly to a point (referred to in 
Chapter XIX.) on which we had had some correspondence. The paper 
had escaped my notice, haying but recently reached the library of our 
Academy of Natural Sciences. " Had I seen this. valuable and interesting 
paper a few months sooner, it would have enabled me to revise and in 
some places correct matters which appear in certain chapters of my book. 
As, however, my sheets are printed, and the type distributed, it is onty 
permitted me to make use of an Appendix Note to call attention to what 
I deem very important. 
Nort A.—On THE SPINNING ORGANS. 
(Cuaprer II.) 
Dr. Apstein, in the paper above alluded to, has wrought out with great 
pains the scheme of study which years ago I had proposed to myself, as 
I have already intimated in my preface. He has observed with care, and 
presented in his plates, the exterior spinning organs of various species 
from the several tribes. He has also made studies and drawings of the 
internal spinning organs. It is most interesting to note both the agree- 
ments and. the differences as thus indicated. I venture to present fac- 
similes of several figures, one giving the spinning organs in situ of Epeira 
diademata, which the reader may compare with my own partially diagram- 
atic figure of Argiope cophinaria, page 39, Fig. 30. I also give some re- 
productions of the spinning spools, which Apstein has been able to locate 
in their connections with the various glands. This identity has heretofore 
been very much in doubt. 
Dr. Apstein believes that the material, which forms the viscid beads 
upon the snares of Orbweayers and some of the Lineweavyers, is secreted by 
the Aggregate glands. He thinks that the Tubuliform glands secrete the 
cocooning stuff, or the threads which envelop the eggs. The curled threads 
* Bau und Function der Spinndritisen der Araneida. Von Carl Apstein. Archiv fiir 
Naturgeschichte, 1889, pages 29-74, Plates IIT., IV., V. 
(357) 
