434 REPORT—1905. 
the same letters, A and a will be allelomorphic characters borne by the corre- 
sponding chromosomes, as are B, 6, C, ¢, &e. The zygote will contain all eight 
chromosomes and characters, but during gameto-genesis allelomorphic characters 
will of necessity become separated into different germ-cells. Ifin the peas originally 
described by Mendel A represents yellow, @ green, and B represents round, 4 
wrinkled, then gametes will be formed consisting of AB, Ad, aB, ab, but A and 
a, B and b cannot coexist in the same gamete. We have, therefore, in the 
observed behaviours of the chromosomes a mechanism which seems exactly 
adapted to bring about a segregation such as is postulated by the Mendelian 
theory, and it seems incredible that there can be no connection between the two 
sets of phenomena. 
The most obvious objection to the hypothesis here sketched is that the number 
of chromosomes is much less than the characters which are inherited. It is 
possible that many characters are borne by a number of chromosomes together, 
and are not inherited in the Mendelian manner. This would account for the cases 
of blended inheritance where segregation does not take place. 
But cases are known where there are more truly allelomorphic characters than 
there are chromosomes, and each chromosome must therefore bear more than one 
such character. . If the chromosome is an individual, these characters must always 
be associated, and cases of correlation of this kind are known. Coupling of 
characters would, however, be much more frequent if this were the complete 
explanation, and we must fall back on the hypothesis that the chromosomes are 
not indivisible units. At first sight this seems to contradict the assumption made 
above concerning chromosome individuality, but the evidence is equally in favour 
of the view that chromosomes are definite aggregates of individuals, which become 
associated together at cell-division. Several cases have been described which 
point in this direction; e.g., Petrunkewitsch states that there are eight chromosomes 
in the female pronucleus of the bee and sixty-four in the blastoderm nuclei. In 
Ascaris, according to Boveri, there are two chromosomes in the fertilised egg, and 
mm all the nuclei in the ‘germ-track,’ but in the somatic nuclei they break up 
into a large number of small units. It seems possible, therefore, that the chromo- 
somes are aggregates of smaller units, which reappear in the same form at each 
nuclear division, but not necessarily composed of exactly the same constituents. 
As an analogy one may compare the chromosomes to boats of various sizes which 
take a party of people across a river; when the people return (representing 
another nuclear division) there will be the same number of boats, each containing 
the same number of people, but it is not necessary that the persons in each boat 
should be the same as at the first crossing, If this hypothesis is true, it involves 
the further assumption that if a character Z is transferred from chromosome A to 
chromosome B, then the allelomorphic character = must at the same time migrate 
from a to 6, for otherwise the pairing and separation of allelomorphs could not be 
effected. Probably, however, the formation and pairing of chromosomes consists in 
the association and pairing of homologous units, and one can be imagined as easily as 
the other. The mosaics which occasionally occur may perhaps be accounted for 
by the arrangement of homologous units in chromosomes of different pairs. 
THURSDAY, AUGUST 17. 
The following Papers and Reports were read :— 
1. Cases of Extensive Mortality among Marine Animals on the South 
African Coast, with Suggestions as to their Cause or Causes. By 
J. D. F. Giecurist, JZ.A., Ph.D., B.Sc. 
In the year 1837 great numbers of fish were cast up on the beach at Table 
Bay. This continued for about three days. Some of the fish were alive. Large 
pumbers of whales were also cast up. In 1880 a still more extensive mortality 
