De 
the different groups increase and decrease their food-yolk in a most 
fantastic and arbitrary fashion. 
In the supposed ancestral history from Cyclostomata to Se- 
lachii along with the enormous decrease in the number of ova re- 
quired, and the large increase in size ef those which ripened, a con- 
siderable amount of ovarial tissue must have become unless. If heredity 
has any influence on the species (a matter certainly not open to 
question), a very large percentage of the ovarial tissue must in course 
of time lose its hereditary tendency to develop. And when the Se- 
lachians began (according to the theory) to evolve the Ganoids, there 
was, with the supposed decrease in size of the ova, a call for a con- 
siderable, nay enormous, increase in their number. Whence came the 
increased production of ova? 
It is one of the tendencies of many recent theorizers to bolster 
up their theory with a new hypothesis, whenever one is required. That 
is, perhaps, a perfectly legitimate proceeding, provided the fact be not 
lost sight of that the hypotheses are hypotheses and nothing more. But 
very often, as soon as the hypotheses demand an increase some of 
them lose their hypothetical characters, and are assumed to be facts. 
How many hypotheses will this repeated increase and decrease 
theory require, before it becomes an accepted fact to the world at 
large in addition to Prof. RABL? 
It is, however, a fact, that the Selachians, even on RAgr’s theory 
of the ancestry of the fishes, undoubtedly the lowest forms with me- 
roblastic and at the same time with few ova (the proviso is im- 
portant as excluding the Teleostei), are also the first forms in 
which a degeneration of (male and female) reproductive tissue is met 
with. Not one of the least brilliant of MiHALKoVvIcs’ discoveries is 
that of the relationship between the reproductive gland and the so- 
called supra-renal bodies. 
MIHALKOVICS !) showed that the non-nervous part of these organs 
is the most anterior portion of the reproductive gland, and that in 
those animals in which suprarenals occur the germinal cells which 
give rise to them have undergone degeneration, and have got separated 
off from the rest of the germinal epithelium as a mass of cells re- 
maining in a so-called embryonic state~ 
It is a significant fact, hitherto I believe unnoticed, that supra- 
1) vy. MisArkovics, V., Entwickelung d. Harn- u. Geschlechtsappa- 
rates der Amnioten. III. Die Geschlechtsdrüsen. Internat. Monatsschr. 
f, Anat. etc., Bd. II, 1885, p. 389— 402. 
