INTERNAL ANATOMY OF THE GAMASIN^. 285 



scutata of Koch, hut the TJropoda ocalis of the same author — an error which did uot 

 arise witli Winlvler, but is C02)ied by him witli a (?) from one of the systematists. 



Besides the literature above referred to, there are two memoirs of my own on the 

 internal anatomy of TJropoda *. In these I explained in what particulars I was uot able 

 to agree with Winkler's description of the anatomy of his species, or perhaps I should 

 rather say what additions I should make to it, and I also showed how widely the intei'ual 

 organization, particularly of the female reproductive organs, varied in ditferent species of 

 the genus. 



The Italian works upon the Gamasida3 are chiefly systematic or biological ; they 

 contain very little information relative to the internal anatomy. 



Objects op this Paper. 



In the paper spoken of in the last section, Winkler, besides treating of the anatomy 

 of his Gamasus crassipes (I shall drop the " so called " in future for the sake of brevity) 

 and one or two otiier species, proceeds to generalize and to take it for granted that other 

 species are similar. I have usually found it unsafe to generalize in matters connected 

 with the Acarina ; this probably is partly due to our imperfect knowledge of the group, 

 and partly to the extreme tendency to vary in an unexpected manner which is found on 

 investigation, not only between different families, but even between different species of 

 the same genus when the internal organs are examined. One of the principal objects of 

 this paper is to show that, although, of course, there is a general resemblance between 

 the viscera of the various species of Gamasidse, which often becomes so marked as to 

 constitute a degree of similarity almost amounting to identity, and although some 

 organs vary but little, yet many most important organs and even systems of the body 

 vary so greatly in ditferent members of the group, and even of the same genvis, that 

 whole sets of organs are found in one which are absent in the other, and that the parts 

 which are strictly homologous are often so developed as to be remarkably different from 

 one another ; this is especially true of the reproductive organs. It has also been my 

 endeavour to delineate and give definite information with regard to such variations and 

 new organs, which have come under my notice, as appear to me to be of sufficient 

 importance and interest to make them worthy of remark. Again, both on account of its 

 great intrinsic interest and, incidentally to the anatomy, in order, as far as possible, to 

 make certain of the exact functions and mode of employment of some of the oi"gaus, a 

 series of observations have been made as to the mode of coition in the species of 

 Gamasids which I have been dealing w^ith. This has not been by any means easy; it 

 has required great care and jj^i-tience ; it is not every species of Gamasus which will 

 copulate in confinement under circumstances which render observation possible ; and 

 even when such a species is obtained and the requisite surrounding conditions success- 

 fully maintained, observation is difficult, and the student must be content to bear with 



* "Observations ou the special Internal Anatomy of Uroj^utla Kramcri," Joiirn. K. ilicrosc. Soc. 1889, pp. l-l-"). 

 " On the Variations of the Female Reproductive Organs, especially tlie Vestibule, in different Species of Urojjoda,'' 

 ibid. 1890, pp. 142-1.52. 



