Chap. XIII.] GONADS OF COCKROACH. 497 



passes into the oviduct, where it is perhaps fertilised, 

 and, further, provided with a coat (comparable to that 

 by means of which the spermatozoa are aggregated into 

 spermatophores), one end of which is drawn out into a 

 short stalk ; by means of this stalk the developing ova 

 become attached to the small appendages of the 

 abdominal region, with which they remain connected 

 till they are converted into the likeness of the adult ; 

 a crayfish, or lobster, at this stage is said to be "in 

 berry." There is, then, no free-swimming larval stage 

 in the fresh-water crayfish. 



In the cockroach, as in the earthworm, the true 

 character of the testes proper has been misunderstood, 

 owing to just the same causes ; it is in young males 

 only that the true testes, which have a dorsal position, 

 can be detected ; in the adult forms their products are 

 found in the reservoir which forms the double head of 

 the single short efferent duct, and as this reservoir is 

 a complicated structure (the so-caRed mushroom- 

 shaped gland), formed of a number of short blind 

 tubes, within which the spermatozoa go through the 

 later stages of their development, it has, not un- 

 naturally, been regarded as the true testis. The 

 matured spermatozoa are thread-like bodies pointed at 

 either end, which exhibit a wavy movement. 



As has been pointed out by Waldeyer, structures 

 are to be seen in the ovaries of the Arthropoda which 

 correspond to the Graafian follicles of the Vertebrata 

 (page 508). 



Gegenbaur is strongly of opinion that the hiass 

 of generative cells in the Arthropoda is primitively 

 single, and adduces many facts in support of this 

 view ; not only, however, is this arrangement contrary 

 to that which obtains in all other bilaterally sym- 

 metrical animals, but it is further opposed by certain 

 embryological facts ; for example, the Lepidoptera 

 (butterflies and moths) have, in the later stages of 

 G G 16 



