APPENDIX. 



While revising the index for this vokime 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, having 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 apj^ear in certain chapters of mj' book. 

 As, however, my sheets are printed, and the tyjse distributed, it is only 

 permitted me to make use of an Appendix Note to call attention to what 

 I deem very important. 



Note A. — On the Spinning Organs. 

 (Chapter 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 Orbweavers and some of the Lineweavers, 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 uud Function der Spinndriisen der Araneida. Von Carl Apstein. Archiv fiir 

 Naturgeschichte, 18S9, pages 29-74, Plates III., IV., V. 



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