432 REPORT—1905. 
V. MADAGASCAR. 
It is extremely remarkable that this great island, which in most groups of 
animals sh ws so many striking features, should in its fish-fauna be one of the 
most insignificant districts in the whole world. For, if we exclude the numerous 
Grey Mullets and Gobies, and a few Perches of the genera Kuhlia and Ambassis, 
which live partly in the sea, and probably mostly breed in salt water, the truly 
fresh-water fish-fauna is reduced to sixteen species—viz., two Silurids, two 
Cyprinodontids, one Atherinid, four Cichlids, and seven Gobiids, the latter, no 
doubt, recent immigrants from the sea. The Silurids belong to two distinct 
genera, Lemonema, allied to the African Chrysichthys, first discovered in Mauritius, 
and Ancharius, allied to the marine or semi-marine Ariws, and, perhaps, also 
entering the sea. Of the four Cichlids two belong to a very distinct autochtonous 
genus, Paretroplus, whilst the two others are respectively referred to the African 
genera Tilapia and Paratilapia. The two Cyprinodontids belong to the widely 
distributed genus Haplochilus. 
In concluding this sketch, whilst looking back with satisfaction upon the rapid 
progress which African ichthyology has Jately made, and expressing our gralitude 
to the Governments, institutions, and collectors to whom we owe this progress, 
we cannot abstain from pointing out how much remains to be done. All the 
great lakes are insufficiently explored, and Bangwelo has never been fished for 
scientific purposes, whilst within the limits of this colony an extensive collection 
from the Upper Zambesi is still a desideratum, and Lake Ngami is drying up with- 
out any of its fishes having been secured forstudy. The fishes of the Congo above 
Stanley Falls, and of many of its northern and all of its southern tributaries, are 
still unknown. But it is gratifying to observe the ever-growing interest in this 
hitherto somewhat neglected branch of zoology, and I may express the hope that 
the next decade will be productive of even greater results than have been achieved 
within the last. The privilege which has been conferred upon me of addressing 
you on this occasion shows the appreciation in which systematic ichthyology is 
held by the zoologists of the British Association. 
The following Paper was read :— 
Recent Work on Gametogenesis and its Bearing on Theories of Heredity. 
By L. Doncaster, M.A. 
Many years ago Weismann put forward the hypothesis that the material bearer 
of hereditary qualities is the chromatin of the nucleus. Recent work has made 
it necessary to revise a large part of Weismann’s scheme, but has confirmed the 
central theory, that the chromosomes are the bearers of inherited characters. The 
most recent work on the maturation of the germ-cells has shown that they contain 
a mechanism which seems precisely adapted to bring about that segregation of 
characters which forms the most fundamental part of the Mendelian theory, and 
it seems hardly possible that the two things are unconnected. 
That hereditary qualities are borne by the nucleus of the germ-cell is shown 
by the fact that the spermatozoon consists of little else, the tail being a motor 
organ, and the middle piece part of the apparatus for cell-division, Further, 
Boveri's experiments on the fertilisation of non-nucleated fragments show that 
when no egg-nucleus is present the inherited qualities of the larva are exclusively 
paternal. 
It is also fairly certain that the chromosomes are the essential part of the 
nucleus in this connection. When an egg (eg., of a sea-urchin) develops 
parthenogenetically only half the normal number of chromosomes are present, 
and yet the larva is normal. But there is evidence that the chromosomes are 
qualitatively different from one another, and that when all the necessary kinds 
are not present in a cell that cell cannot develop further. This is shown by 
