214. PROF. HUXLEY ON THE AGAMIC REPRODUCTION 



slender extremities of the eight oviducal and uterine tuhes proceed," and which are supposed 

 to be ovaries, I am at a loss to divine. There are no such bodies, that I can discover. 



In the latter part of the same citation, the existence of a histological difference between 

 the contents of the jiseudovariuni and those of the ovarium is asserted. But there is 

 assm-edly nothing in the former to Avhich the description can apply ; and I re-affirm the 

 impossibility of di-awing any histological line of demarcation between the pseudova and 

 the young true ova. 



How any one who carefully studies the development of Aphis can arrive at the con- 

 clusion that a portion of the germ-mass is taken into the body of the embryo Aphis, " like 

 the remnant of the yelk of the chick," I know not ; and, for the reasons mentioned above, I 

 even doubt if I clearly apprehend what is meant. Dr. Burnett {I. c. p. 73) assumes that 

 what is intended by " portion of the germ-mass" is what I have termed the pseudovitellus. 

 In that case the statement is erroneous ; for the pseudovitellus takes no share in the for- 

 mation of the pseudovarium. If, on the other hand, the true rudiment of the pseud- 

 ovarium is indicated, the statement in question is equally incorrect ; for this is never out 

 of the body, and hence can hardly be taken into it, nor can that out of which the so- 

 called " oviducts" are pi'oduced be properly said to become " connected with them," or to 

 " aid in forming their filamentary extremities." 



"When the basis of a hypothesis is shown to be incorrect, the hypothesis itself is com- 

 monly considered to be disposed of ; but possibly in the present case it may be urged that, 

 although the contents of the pseudovarium are wholly dissimilar "to the germ-mass in 

 in its state of minutest subdivision," they are nevex-theless so little changed that my 

 criticism of the phi'ase is trivial. To this I reply that, whether the alteration be small or 

 great, it is as great as that which occurs in the terminal caeca of a gland, or in a true 

 ovarium, and that the tissue of the apical pseudovarian chamber is far more diiferentiated 

 than the indifferent tissue which constitutes the youngest portion of an ordinary epithelium 

 or epidermis. 



Whatever conclusions are based upon the resemblance of the tissue of the pseudovarium 

 to that of the embryo, must therefore apply in equal or greater force to the tissues which 

 I have just named ; and, unless reason can be shown to the contrary, whatever powers are 

 2)0ssessed by the one, in virtue of this similarity, must be possessed in equal or greater 

 degree by the other. 



But in this case what becomes of the hypothetical explanation of the asexual reproduc- 

 tion of A2}his, under chscussion ? 



The condition of such reproduction is, according to the hypothesis, the retention of 

 "certain of the progeny of the primary impregnated germ-cell unchanged," "with so 

 much of the spermatic force, inherited by the retained germ-cells from the parent-cell or 

 germ-vesicle, as suffices to set on foot and maintain the same series of formative actions 

 as those which constituted the individual containing them." 



Let us imagine, for the sake of argument, that the amount of histological change in 

 the pseudovarian mass is imimportant. I am ready to suppose even, in accordance with 

 the hypothesis, that its cells retain sufficient "spermatic force" (wliatever that may be) 



I 



