926 
Proceedings of the Royal Society 
Just as some zoospores may sometimes dispense with conjugation 
and germinate independently, so may ova develop parthenogeneti- 
cally. These are to be regarded as incompletely differentiated forms 
which retain a measure of kataholic (male) products, and thus do 
not need fertilisation. Such a successful balance between anabolism 
and katabolism is indeed the ideal of all organic life. That the 
extrusion of polar globules has been observed in some instances, 
only shows that some kataholic products are still expelled. Just as 
in the disappearance of sexual reproduction in parasitic fungi, where 
surrounding waste products presumably serve the purpose other- 
wise effected by means of sexual organs, so peculiarities in the develop- 
ment of parthenogenetic ova may explain the retention of the normal 
balance which makes division possible without the usual stimulus 
afforded by fertilisation. 
(5) The deductive interpretation must, however, be extended from 
the elements themselves to the associated tissues. In the present 
state of our knowledge, it is sufficient to suggest the interpre- 
tation of the phenomena of segmentation, or of the resemblances 
and divergences between that of the ovum and that of the spermato- 
gonium. That the different modes of segmentation, in regard to 
which we barely know the morphological facts, must ultimately 
depend upon variations in the anabolic and kataholic rhythm is evi- 
dent, though the nature of these variations is obscure. Nor in regard 
to later development can we do more than note that the physiological 
importance of the embryonic layers may be essentially expressed in 
terms of their respective predominance of anabolism and katabolism. 
(6) In reference to the tissues of ovary and testis, tempting appli- 
cations might be suggested. Hermaphroditism, for instance, is 
common in the undifferentiated embryonic stages, when the cell- 
diathesis is still to some extent undecided. Whether it occurs 
thus, or with casual or constant persistence in the adult, it is due 
to the local preponderance of anabolism and katabolism in one set of 
reproductive cells or in one period of their life. Yan Beneden and 
others have suggested that the yolk -bodies ( vitellaria ) of the com- 
plex generative organs of many Platyhelminthes are to be regarded 
as degenerate ovaries. On the present view this seems extremely 
probable, and is expressible as the result of an over-nutrition result- 
ing in a too completely anabolic preponderance. Other pathological 
