28g K. KISHINOU^E 



dao-es make their appearance in these five segments as small round 

 knobs. The cœlomic cavities of the same segments are just below the 

 evaginations for the appendages. 



In the next stage the segment of the chelicerie is cut off from the 

 cephalic lobe, and three new segments are added between the last seg- 

 ment and the caudal lobe (Fig. 2). By this time the cephalothoracic 

 appendages have become much elongated, and the mesoderm has spread 

 into them. The cœlomic cavity extends to the distal end of each 

 appendage ; in fact the larger part of the cavity is now found within 

 the appendage. It spreads a little at the base of tlie appendage, so 

 that three portions may be distinguished in it in a cross section of 

 the embryo (Fig. 5) as Schimkewitsch* observed — one portion in 

 the appendage, a second extending a little in the dorsal direction, 

 and the third extending a little ventrally. The last two are the 

 horns of the basal enlargement. In the abdominal region, the pro- 

 visional appendages are not yet formed ; but the mesodermic somites 

 develop rapidly, and in each of the first and the second abdominal 

 segments a pair of cœlomic cavities is produced. Thus seven pairs of 

 the cœlomic cavities are now found. 



Subsequently two more new segments are added between the last 

 formed segment and the caudal lobe. A pair of the cœlomic cavities 

 is formed in this stage in each of the following segments: the cephalic 

 lobe, the segment of the chelicerae, and the third to the seventh 

 abdominal segments (Fig. 4). These seven newly formed pairs of 

 cielomic cavities together with the seven pairs already existing make 

 in all fourteen pairs, the caudal lobe alone being now devoid of any. 

 In tlie cephalic lobe the mesoderm is not divided into two lateral 

 parts, therefore the two cœlomic cavities, right and left, are separated 



* Étude sur le Uéveloppement des Araigaées. Arch, de Biologi . Touie XT. 1887. 



