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in close contact still with the voluminous 

 yolk sack, neither mouth opening nor 

 under jaw or gill-slits are present as yet. 

 The eyes are without pigment. The rudi- 

 ment of the organs of equilibrium are 

 present as two vesicles, each with two 

 statoliths in it. The beating of the heart 

 has begun within the egg already. 



A considerable lengthening occurs 

 during the first hours after hatching, so 

 that soon after the embryo nearly reaches 

 the length of the one reproduced in 

 figure 4, which, however, is old already 

 48 hours. The yolk decreases gradually, 

 the oil-globules become smaller. The head 

 is freeing itself from the yolk, the rudi- 

 ments of the gill-slits and of the mouth 

 become visible. The beginning of the 

 pectoral fins makes its appearance be- 

 tween the 3rd and the 4th myotome 

 (Fig. 4, p.f.). 



Characteristic of all the larvae of 

 Clupea-WkQ fishes which I have reared 

 until now from pelagic eggs taken in the 

 Java Sea is the crossed arrangement of 

 the muscle fibres in the myotomes, as 

 i have tried to denote in Fig. 4, In newly 

 hatched larvae already this peculiarity may 

 be noted. The muscle fibres do not, as 

 is the case e. g. in eel-like fishes, run 

 parallel to the longitudinal axis of the 

 animal, but in two directions intersecting 

 each other. A closer examination with 

 higher and deeper focussing of the micros- 

 cope teaches that the muscle fibres are 

 arranged in three layers, a superficial one 

 restricted to the lowerhalf of the myotome, 

 a middle layer reaching from the upper 

 to the lower border of the myotome, and a 

 deeper one restricted to the upper half. 

 In the middle layer the muscle fibres run 

 in a direction from the anterior lower to 

 the posterior upper corner of the myotome, 

 in both the superficial and the deeper layers 



