APPENDIX V 309 



The animals, however, prove after all to be hermaphro- 

 dites. Since the last careful study of Apus cancriformis^ as a 

 whole, by Zaddach in 1841 (the works of Ray Lankester 

 and others deal only with special points), new methods of 

 research have been introduced into our laboratories which 

 reveal details not easily discoverable by the older methods. 

 Zaddach's figures of the ovaries and testes of Apus are thus 

 naturally somewhat deficient — as deficient, indeed, as the 

 best work we can do to-day will, we hope, be found to be 

 fifty years hence. 



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In my preliminary notice {Jenaische Zeitschrlft filr 

 Naturwissenschaft, Band xxv., N.F. xviii.) announcing 

 the hermaphroditism of L. Spitzbergensis, knowing how 

 much the reproduction of the Apodidae had been dis- 

 cussed, I ventured to assert that in all probability the 

 other species of the genus would also prove on closer 

 examination to be hermaphrodite. As above stated, I 

 found the sperm-forming centres in L. glaciafis in identically 

 the same position as in the Spitzbergen variety. By 

 the kindness of Professor Mobius, the Director of the new 

 Berlin Museum, and of the Rev. Canon Norman, I have 

 also been able to examine Apus cancriformis and Lepidurus 

 productus. In both these the sperm-forming centres 

 were found scattered here and there among the rich 

 branchings of the segmental diverticula of the genital tube. 

 They occur either at the tips of such branches, where the 

 eggs ordinarily develop, or as slight lateral bulgings of the 

 same. In all cases the spermatogenesis is the same, the 

 epithelium breaking up into sperm-cells ; these escape into 

 the lumen of the tube, and are found in considerable 

 numbers near the genital aperture, where the epithelial 

 lining of the tube is hardly demonstrable, the walls of the 

 tube consisting of a fibrous membrane, in the folds of which 



