24 Gen. Sub. 
GENERAL SUBJECTS. 
one time to the weight of the rest of the fish. Instances of the very 
different degree of ease with which the ova are carried in different 
species. In most cases it would be quite impossible for the fish to carry 
simultaneously, in the mature condition, all the eggs which the condi- 
tions of the struggle for existence have made it imperative it should 
produce. Perhaps this explains : (1) why among most sea-fishes there is 
a general, and sometimes a great, preponderance of females. On the 
other hand, among fish with demersal ova extruded in large quantities 
the males predominate. Perhaps the above-mentioned fact also explains 
(2) the generally larger size of the female fish, and (3) the more or less 
sudden increase of bulk which occurs in the ovum shortly before extru- 
sion. Proportional number of ova produced by different species. Varia- 
tion in fecundity in individuals of the same species. 
Fredericq, L. Ueber Autotomie. Arch. Ges. Phys. xv, pp. G00-G02. 
Fuenzel, J. Ueber die Selbstverstiimmelung (Autotomie) der Thiere. 
T. c. pp. 191-214. 
Illustrations of the wide occurrence of autotomy ; its restriction to 
definite predisposed regions of the body ; its real causes not yet analysed. 
Gkuvel, A. De quelques ph6nom&nes de reproduction chez les Cirrhi- 
pfcdes. C.R. cxiii, pp. 707 & 708. 
Usually reciprocal fecundation in Cirripedia. Where this is impossible, 
there may be self-fecundation, as seems to occur in Pollicipes. 
Hartog, M. M. Abstract of Maupas’s Researches on Multiplication and 
Fertilisation in Ciliate Infusorians. Q. J. Micr. Sci. xxxii, pp. 
599-614. 
IIartog, M. M. Some Problems of Reproduction : a comparative study 
of gametogeny and protoplasmic senescence and rejuvenescence. 
Op. cit. xxxiii, pp. 1-79. 
In absolutely agamous forms of Monadinece rest is the only agent of 
rejuvenescence. In apogamous and self-fertilising organisms change of 
the mode of life is a frequent mode of rejuvenescence. In higher 
Monadinece and Myxomycetes the cytoplasm is renewed by plastogamy. A 
step in advance, involving karyogamy, is isogamy, plural and binary. In 
rejuvenescence the karyogamy is due to the fact that the zygote nucleus 
and cytoplast form a new cell-association. Illustrations of the manner in 
which other modes of rejuvenescence may replace the karyogamy of 
gametes. Those organisms that have attained the capability of kary- 
ogamic rejuvenescence may, by prolonged fissile reproduction without 
karyogamy, pass into a senile condition marked by reproductive incapacity. 
Rapidly repeated nuclear fissions, without sufficient interval for nutrition 
and recovery, may lower the vital energy of the cell, and accelerate this 
reproductive incapacity ; but this is a matter of constitutional tempera- 
ment. A further evolution of this constitutional weakness takes place in 
