INTERNAL ANATOMY OF THE GAMASIN.E. 291 



the two species, both are developments of the ring- system upon which the genitalia of 

 botli sexes in the Acarina, and, indeed, in other groups of llie Arachuida, are so 

 frequently based ; but this is not saying much, for the varieties which nature gives us iu 

 tliis ring are so numerous and so diverse that they woidd scarcely seem greater if based 

 upon a separate plan. 



Winkler mentions that the distal portion of tlie ductus ejaeulatorius is coated with 

 ehitin. In G. terrihiUs this eliitiuons coating rather assumes the form of a short 

 ehitinous trough, not entirely surrounding the mouth of tlie ductus, but iu \\ hieh tbe 

 latter lies ; while a ]Kvrtial ehitinous ring, like one of these in a pseuilo-traehea of the 

 bloAV-fly's tongue, is found within the mouth of the tube; the reason for this dill'ereuee 

 may possibly be the size of the bodies that have to pass through the ductus ejaeulatorius 

 of G. Icrrtliilis. 



It may be as well to say a few words as to the maturation of the sperm-eKMueuls iu 

 this testis, particularly as it ail'ects later portions of this pai)er. 



In the attenuated end of each testis, from the part wliere it joins its fellow of the 

 opposite side for a short distance onward, we tiiul, inside the tunica pn)[)ria, A:c., which 

 covers the whole organ, a closely-packed quantity of cells, which at tlu> narrowest part 

 are extremely small and gradually increase in size; but in each cell, wherever it is 

 amenable to the microscope, we sec the nucleus quite clear and distinct; allliough iu 

 the smaller cells it is scarcely possible to see a nucleolus. As we examine (lie ti>stis, 

 ]n'oceeding toward the ductus ejaeulatorius, the cells gradually and steadily incnvise iu 

 size, until we arrive nearly at the point wh(M'(> what I have spoken of as the more 

 perpendicular portion joins the horizontal part. Near this point the cells, which we 

 may call " sperm-mother-cells,"' have attained a remarkable size, some of them nu-asure 

 as much as 1.70 ^1X125 jt*; (>aeh cell still retains a large clear nucleus, whicli in a cell ol' 

 the above m(>asunMncnt would be about oS |!^ and woulil possess a well-niiu'ked nucleolus 

 of about- 2r);i. Hefore the niother-eell bad attained this size a number of n\inule, nearly 

 i^lobular bodies, ch^ar but highly refractive, and not at lirst measuring more than 1 a to 

 2;u, will have formed in contact witli tbe iiuun- side of thi> iHM'i])heral protoplasm ; these 

 I consider to be the true spermatozoa in an i-arly stage. Wluni the cell has aKained its 

 full siz(> the interior of the i)eripheral protoplasm is nearly coated with tbeni; tbe cell, 

 bowevei', still remains fairly transparent, or al least translui-ent. 'i'be nncleolns has 

 already shown signs of brc^aking up. 



On iiassini;- from tb(> ))er])endicnlar to the; horizontal i)art of the testis a great change 

 takes place in tbe sperm-motber-cell, its nucleus breaks up entirely, or sinks into the 

 centre of the cell; tlu< sptu'matozoa break olf from the peripheral protoplasm and collect 

 in a mass in the middle of the cell ; this mass is closely agglomeraU-d and no longer 

 transparent, and a clear space is left belween it and the peripheral protoplasm ; tbe whole 

 cell now presents the appearance of a parlially-lilled spermatocyst. The sjxTnialozoa 

 continue to inerciuse slightly in size, until in tbe ripe ei'lls nt>arest to the vasa (h^ferentia 

 they may nuMsun; W n to 1;.; tbe sperm-motber-cell itself has, however, shrunk a little, 

 ami iu a testis where the largest uujthcr-eells were of the above measurement tbos(> fully 

 ripe would not exceed about 135 /. X 8'J /.. These measurements are taken all 1 brough from 



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