AND MORPHOLOGY OF APHIS. 213 
unchanged. One sees such portion of the germ-mass taken into the semitransparent 
body of the embryo Aphis, like the remnant of the yelk in the chick. TI at first thought 
that it was about to be enclosed within the alimentary canal, but it is not so. As the 
embryo grows, it assumes the position of the ovarium, and becomes divided into oval 
masses and enclosed by the filamentary extremities of the eight oviducts. . . ." — Zbid. 
p. 69-70. 
* [t would be needless to multiply the illustrations of the essential condition of these 
phenomena. That condition is, the retention of certain of the progeny of the primary 
impregnated germ-cell, or in other words, of the germ-mass unchanged, in the body of 
the first individual developed from that germ-mass, with so much of the spermatic 
force inherited by the retained germ-cells from the parent cell or germ-vesiele as 
suffices to set on foot and maintain the same series of formative actions as those which 
constituted the individual containing them.” —Tbid. p. 72. 
“The physiologist congratulates himself with justice when he has been able to pass 
from cause to cause, until he arrives at the union of the spermatozoon with the germinal 
vesicle as the essential condition of development—a cause ready to operate when 
favourable circumstances concur, and without which cause these circumstances would 
have no effect. 
What I have endeavoured to do has been to point out the conditions which bring about 
the presence of the same essential cause in the cases of the development of an embryo 
from a parent that has not itself been impregnated. The cause is the same in kind, 
though not in degree, and every successive generation, or series of spontaneous fissions, 
of the primary impregnated germ-cell, must weaken the spermatie force transmitted to 
sueh successive generations of cells. 
“The force is exhausted in proportion to the complexity and living powers of the 
organism developed from the primary germ-cell and germ-mass.”—1bid. pp. 72, 73. 
These statements are repeated in the recently published second edition of Prof. Owen's 
Lectures on the Invertebrata. l 
The paragraphs I have cited contain two kinds of propositions—assertions with respect 
to matters of fact, and deductions from those assertions. The former are, according to my 
observations, incorrect; and, as I conċeive, the latter are unfounded. 
As regards the first citation, for instance, the contents of the apical chambers ef the 
pseudovaria are not by any means identical with those * resulting from the final subdivision 
of germ-cells retained unchanged," as the most cursory comparison of the two structures 
will show. ; 
In the second citation it is affirmed that the germs are perceptible in the embryo before 
any organs are formed for their reception. This, again, is an error if my observations ped 
correct. "The absence of figures, and the too vague and general character of the descrip- 
tions in Prof. Owen's work, render it very difficult to understand what lie really has seen; 
but I imagine that he has taken the substance which constitutes the rudiment of the whole 
pseudovarium, and which becomes differentiated partly into pseudova, partly into tur walls 
- of the organ, for a mass of germs. What is meant by “those two bodies €— the 
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