74 



segmentation. Muscle-fibres are scarcely found. There are only three 

 pairs of appendages. They are short unsegmented, blunt at the distal 

 end and are rather club-shaped. The second pair is the longest, the 

 first pair is next in length, and the third pair is the shortest. The first 

 pair (bristles excluded) is about */ 2 so long as the body, and is unira- 

 mous, while the others are biramous. Each appendage has some brist- 

 les near the distal end. The appendage of the first pair has 1 short and 

 3 long bristles, that of the second pair 1 short and 2 long bristles on 

 the inner branch, 5 or 6 long bristles on the outer branch, and that of 

 the third pair 3 long bristles on each branch of it. I could not find 

 the cilia on these bristles and also on the paired bristles at the posterior 

 end of the body. 



In the next stage which I had observed, all the appendages were 

 much elongated and became gradually narrow towards the distal end. 

 This stage, however, was not minutely examined, so I can not give more 

 detailed description. 



In a little older larva (fig. 2) , the appendages are divided into 

 numerous, minute segments. Bristles on the first two pairs of appen- 

 dages have increased in number. The posterior end of the body is 



faintly bilobed. On each 

 lobe, there is a very long 

 bristle which was already 

 found in the youngest 

 Nauplius. On either side 

 of this long bristle, there 

 is a short bristle and outer- 

 most to these three brist- 

 les, we find a rudiment of 

 another bristle as a poin- 

 ted protuberance. All 

 the bristles, except small ones, are ciliated. Muscles in appendages 

 and their adductor muscles are now well developed. Behind the third 

 pair of appendages, four pairs of appendages newly appear as short pro- 

 tuberances. 



In this stage, the body is developed posteriorly. It is now about 

 Y 3 mm in length. Behind the third pair of appendages and the upper 

 lip, the ventral side of the body is concave. This is due to the incur- 

 vation of the body towards the ventral side, as it elongates at the 

 posterior end. 



In a little older stage, the animal undergoes a remarkable change. 

 The body is divided into two different parts. The division takes place 

 near the posterior end of the dorsal side by a transverse fold of the 



fig. 2. 



