724 
The Philippine Journal of Science 
1921 
pectorals (Plate 1, fig. 1&). The pectoral fins of the male there- 
fore differ in shape from those of the female. The pectoral fins 
are, relatively, one to one and a half times the length of the head 
in the male and half that in the female. The dorsal, the ventral, 
and the anal fins of the males are also relatively longer than those 
of the females, but they are not so remarkable as the pectoral fins. 
It is well known that among many of the higher animals the 
sexes differ in size. (2) Thus in fishes the male generally ave- 
rages smaller than the female. In loaches the males are so 
markedly smaller that in some cases they are not even half the 
size of the females. The difference in size of male and female 
loaches, obtained by measuring 100 specimens of each sex, is 
shown in Table 1. 
Table 1 . — Measurements of loaches, one hundred specimens of each sex. 
Length of body. 
Male. 
Female. 
Average 
mm. 
101.27 
120. 00 
mm. 
110.02 
150.00 
Maximum 
The body and fins of the male are, to all appearances, well 
adapted in size to active motion in the water. It will be interest- 
ing to investigate the nature and possible use of the spindly swell- 
ing on the back of the male loach. 
MICROSCOPICAL OBSERVATION 
The preparations were fixed in formalin and stained in hse- 
matoxylin eosin. Preparations from the corresponding parts 
of females were also made. According to my observation of the 
swelling, the male differs from the female in the following points : 
The epidermis of the corresponding part of swelling of male 
preparations is thickened and contains many so-called Kolbzelle. 
The dermal scale pouch ( Schuppentasche ) is enlarged and 
contains gelatinous tissue and fat cells. 
A more remarkable adipose tissue is found between the der- 
mal and muscle layers. Many melanin pigment cells are found 
among the fat cells. This adipose tissue has no noticeable cap- 
sule of connective tissue. 
I paid special attention to the swelling to learn whether or 
not it is caused by a strong development of muscle layer, by which 
the ductus deferens might be compressed; my observation led 
to a negative answer. The true nature of such an adipose tis- 
