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skin. The dorsal surface of the anterior portion is the rudiment of the 

 future carapace. This and the following stage may be grouped as 

 Metanauplii. 



Subsequently, the body is faintly segmented. Such segments are 

 found behind the third pair of appendages (fig. 3). There are four 

 segments, corresponding to the fourth — seventh pairs of appendages. 

 These appendages have developed much; but they perform no definite 

 function yet. 



The portion of the body, not-covered by the rudimentary cara- 

 pace has become long, but it is still bent much towards the ventral 

 side. The accompanying figure shows an animal, the tail portion of 



fig. 3. 



which was straightened by the pressure of a cover-glass. The upper 

 lip is comparatively large. Bristles on the first two pairs of appendages 

 have increased in number as well as in length. The masticating por- 

 tion of the third pair of appendages, which becomes the chief portion 

 of the future mandible, is developed as a short cylindrical knob at the 

 base of the appendage. 



In certain species, the posterior margin of the carapace was found 

 in this stage a little thickened and elevated. 



When such a Metanauplius undergoes a moulting, the incurvated 

 tail portion becomes straight and moreover it is greatly elongated near 

 the end. In this way a Metanauplius is transformed to a Protozoea. 

 Tokyo, Nov. 4, 1899. 



6* 



