Ill 



me it is clear from Roule's description that he has mistaken a stage 

 at which the nuclei had already reached the surface for the stage im- 

 mediately succeeding fertilization. This »cicatricule« is apparently 

 the anläge of the blastoderm and his »ilots de blastolécithe« are the 

 remaining cells scattered ovBr the surface of the yolk. This failure 

 to perceive the true significance of these structures is undoubtedly 

 due to his imperfect methods, under which, as he himself states »les 

 éléments diminuent de volume, et leurs noyaux se condensent à l'excès, 

 en faisant disparaître, d'habitude, la plupart des détails de leur struc- 

 ture«. Further comment seems unnecessary. 



Bobretzky's account of the telolecithal segmentation of Oniscus 

 is manifectly unsatisfactory and J. Nusbaum's opinion as to its oc- 

 currence in Porcellio seems to be founded entirely on conjecture. 

 The fact of the undoubted occurrence of the centrolecithal method in 

 the four Oniscidae I have studied, (not to mention its probable occur- 

 rence also in Ligia) , and their agreement in this respect with the 

 AselUdae and with the majority of Crustacea are strong arguments in 

 favor of the universality of the method throughout the entire group of 

 the Isopoda. 



I find my observations on the development of Porcellio at variance 

 with those of M. Roule in several other respects. I shall not 

 however consider these here; they will be more readily understood 

 from the detailed account of my results. 



University of Michigan, Ann Arbor, Mich. U. S. A., Dec. 31, 1894. 



2. Zur Kenntnis der myrmekophilen und termitophilen Arthropoden. 



Von E. Was mann, S. J. (Exaeten bei Roermond, Holland). 



eingeg. 15. Januar 1895. 



Der innige Zusammenhang zwischen Morphologie und Biologie 

 ist auf wenigen zoologischen Forschungsgebieten so auffallend wie bei 

 den sogenannten Gästen der Ameisen und Termiten. Die mannig- 

 faltigsten Formen der Symbiose, vom echten Gastverhältnis (Myr- 

 mecoxenie Emery's) bis zum bloßen Synoeketismus oder zur Myrme- 

 cophagie und zum Parasitismus treten uns hier entgegen und finden 

 oft ihren klaren morphologischen Ausdruck in der Körpergestalt oder in 

 bestimmten Organbildungen, die nur unter dieser biologischen Rück- 

 sicht verständlich werden. So sind z. B. bestimmte Büschel gelber 

 oder rothgelber Haare bei myrmekophilen Coleopteren ein sicheres 

 Zeichen, daß dieselben an den betrefienden Körpertheilen eines äthe- 



haematoxylin and washing in acid alcohol until all the stain is removed from the 

 yolk. Then clear in oil of cloves and examine as a transparent object. 



7* 



