354. ALFRED GIBBS BOURNE. 
Specimen. | Length. | N maa ig | Gamntrasemee Total. Remarks. 
1 170 mm, 140 | 15 155 
2 UD Dita, 168 -— 168 
3 180"; 148 | 12 160 
4 ie reer 91 26 117 | Abnormal. 
5 920 ,, 143 56 199 
6 i Ui 172 | _— 172 
7 15017, 170 | — 170 
8 il See 133 | 44, 177 
9 150°" ;; 140 | — 140 
10 1D ke 115 | 114+ 6 132 | Twice injured. 
ll 05 asf 146 | 10 156 | Apparently still 
growing. 
12 190 _,, 163 | 36 199 
13 95 vis 84. | 40 124 | Still growing. 
caves, 109 6 115 | Still growing. 
15 120°-;, 160 | — 160 | - 
16 140 ,, 140 24. 164 
17 160"; 139 37 176 
18 120) 559 164 ~- 164. 
19 IBD F5,. | 164. _ 164. 
20 145 ,, | 157 — 157 
21 Dp? sa 150 — 150 
22 ay aay 172 -- 172 
We get an average number of segments in the specimens 
which had not been injured of 162, and in those which had 
grown new tails of 156, or, omitting Nos. 13 and 14 which 
were still growing, and No. 10 which had been twice injured, 
-and No. 4 which was abnormal, the half segments on one side 
not always corresponding with the halves on the other side, we 
get an average of 16] segments in an injured worm to corre- 
spond with the average of 162 segments in an uninjured one. 
Segments.—I have spoken above of their number. Some 
importance attaches to the variation in size of the anterior 
segments (compare figs. 1 and 6 with figs. 5 and 12). Annu- 
lation of the segments, which depends upon a particular 
arrangement of the circular muscles, is characteristic of groups 
of species. 
Prostomium.—This presents no easily recognisable varia 
tion in the group (see M. grandis—prostomium, p. 309). 
Setx.—The length varies in the group (my species) from 
