NOTES ON AN AMPHIOXUS OBTAINED IN AMAKUSA, KYUSHYU. 131 



Body 

 length. 



No. of 

 segments in 

 the 

 anterior 

 rogioD . 



No. of 

 segments in 

 the 



middle region. 



No. of 

 segments in 

 the 

 posterior 

 region. 



No. of 

 segments be- 

 hind the com- 

 mencement 

 of the 

 dorsal end of 

 the tail fin. 



No. of 

 segments be- 

 hind the com- 

 mencement 

 of the 

 ventral end of 

 the tail fin. 



Specimens possessing G3 segments in all. 



501... 

 43 ... 

 39i... 

 38 ... 

 37 ... 

 34 ... 

 30f.. 



m- 



... 37 ... 

 ... 36 ... 

 ... 36 ... 

 ... 35 ... 

 ... 36 ... 

 ... 36 ... 

 ... 35 ... 

 ... 36 ... 



... 16 ... 

 ... 17 ... 

 ... 17 ... 

 ... 17 ... 

 ... 17 ... 

 ... 16 ... 

 ... 17 ... 

 ... 17 ... 



... 10 ... 

 ... 10 ... 

 ... 10 ... 



... 11 ... 



... 10 ... 



... 11 ... 

 ... 11 ... 



... 10 ... 



... 11 ... 

 ... 11 ... 

 ... 11 ... 



!" h 



... 12 ... 

 ... 11 ... 



... 17 

 ... 18 

 ... 18 



..." 17 

 ... 17 

 ... 16 



Specimens possessing 62 segments in all. 



5H... 



... 36 ... 



... 17 ... 



... 9 ... 



... 10 ... 



... 14 



Thus the dorsal origin of the tail-fin is in 28 cases out of 48 at the 

 dorsal end of the dorsal arm of the hindmost segment of the middle 

 region, and in 13 cases at the same end of the foremost segment of the 

 hind region, while in 6 out of the remaining 7 cases, it is 2 segments, 

 and in the other, 4 segments, before the anterior end of the postanal 

 region. The place where the anterior end of the ventral part of the 

 same fin commences is in 20 cases 7 segments, and in 19 cases 6 seg- 

 ments, before the anterior end of the hind region, whereas out of the 

 remaining nine cases, in five it is 8 segments, in three 5 segments, and in 

 one 9 segments, before the same part of the animal. From these 

 observations it is to be concluded that the dorsal origin of the tail-fin 

 is in most cases 1 segment, and its ventral end 6 — 7 segments, before 

 the hind section of the body. 



By referring to Table IV it will be seen that the total number of the 

 segments composing the left side of the body varies between 62 and 66, 

 but in the majority of cases 64 seems to be the normal number, for that 

 is the case in 46 specimens out of 58. And it is also to be noted that 



