248 TREUBIA VOL. II, 2—4. 
the formative yolk the first, meridional cleavage took place within the hour ; 
13/, hours after fertilization also the second cleavage had been completed; 
2'/, hours after the fertilization the next two cleavages took place thus 
completing the third stage of segmentation, whilst finally about 3'/, hours 
after fertilization the 5th and 6th cleavages completed also the 4th stage 
of segmentation and the germinal disk then consisted of 16 cells. About 
two or three times 24 hours after fertilization the heart begins to beat and 
the circulation of the blood may be clearly observed. At that time the 
embryos also already begin to faintly beat their tails. | 
When the embryos are a few days older they continually wave the 
pectoral fins and the caudal fin. These fanning movements generally 
grow stronger as the embryos grow older. Furthermore the older embryos 
often turn round within the egg-capsule by one blow of the tail. Probably 
all these movements subserve the exchange of gases. It is a comical thing 
to see the older embryos, watched through somewhat higher powers (e.g- 
through the binocular microscope of Zeiss with the pair of objectives (a; 
and the Huygens’ oculars no. 3) suddenly roll their big eyes in a skittish 
frightened way, often looking at the observer with an inimitable squint. 
As to the period of incubation of the eggs 
of Maplochilus javanicus, | have the following 
data at my disposal. On a female Haplochilus 
javanicus living in an aquarium a cluster of eggs 
were found hanging from the genital opening 
(November 1ith, 1919), which eggs on being 
removed from the 
Fig. 23. Two specimens genital opening, 
from a cluster of eggs found proved to be in pos- 
hanging by the genital open- 
ing of a female Haplochilus Session of anumber 
javanicus (BLKR.) from the of oil-globules, not 
Batavia empangs, living in an : bate 
aquarium. Fertilization took yet united into a 
place but a few hours ago. single olobule. Fur- 
Oilglobules not yet united HS 
into a single globule. X 16!/.. thermore all these Fig. 24. The eggs of fig. 23,a 
eggs showed a ger- little more than 24 hours after 
minal disk consisting of hardly more than 32 RS NL 
cells. In connection with what was communicated 
above concerning the time required in Haplochilus 
panchax after fertilization before the first, second 
and following segmentations take place, I think 
| am warranted in concluding that the fertilization 
of these Maplochilus javanicus eggs had takeri 
place but a few hours before they were per- 
Mois 25) hes eggs: jor ; 
fig. 23 and 24 a little more ceived. Moreover, seeing the animals were fed 
than 2 times 24 hours af- : : 
eee On AT and observed every morning, it may be considered 
