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nation, however, is much more difficult with these, as first of all the skin 
of the embryos of reptiles is not constructed of two layers of epi- 
dermic-cells only, but especially because these cells are much smal- 
ler, so that the directions of the cell grouping and the stages of 
division are much less visible than in the amphibian-skin with its 
large cells. Yet I succeeded at last in preparing large pieces of the 
skin of young embryos and in examining them entirely. Though 
my research on this subject is only in its first stage, I could state 
already that similar rhythmical growths appear in the skin of reptile- 
embryos, which coincide with the pigmentation. The development 
of the bodyform and with this the growth of the covering skin is 
much more complicated than in the generally simple cylindrical or 
barrel-shaped larvae-of the amphibians. Many remarkable and impor- 
tant problems arise of this complication. “It is evident that by 
preference those embryos are examined, that show peculiarities in 
their coat-patterns. 
Thus I examined in the first place the embryos of Draco volans, 
of which a large number of very different ages were collected by 
Dr. L. pr Bussy, at Medan, and presented to the Zoological Museum 
at Amsterdam. These embryos show a very clear and characteristic 
design, of which only a very indistinct image is left in the grown-up 
animals. First of all it may be stated that the design in question 
is quite independent of the metameric architecture of the rest of 
the body. This strikes us most in the design on the membrane 
between the prominent 5 or 6 ribs. In young embryos we see the 
appearance of 4 or 5 dark broad stripes which run obliquely across 
the ribs and thus cross the bloodvessels and nerves, which lie 
alongside the ribs (Fig. 3). We have probably to 
deal with a case of rhythmical, wavelike growth 
of the skin. Already at the first appearance these 
stripes appear as continuous pigment-zones in the 
intercostal membrane. A quicker growth and a 
coinciding pigment formation take place there. The 
whole pattern on this membrane seems to me a 
typical illustration of the fact that this design is 
nothing but a consequence of the rhythmical skin- 
growth. Also on the rest of the body of young 
embryos of Draco volans, one finds a distinet con- 
nection between the first appearing design and the 
Fig. 3. places of strongly developed growth. Large ribbed 
scales appear very early along the flanks of the body and they 
remain when the animal is adult. These scales, whose place does 
