238 MR. E. 8. RUSSZLL ON THE SHELL-GROWTH [Mar. 2, 
males and 21 females. They were collected for the most part 
near Gourock. The males are apparently about three times as 
numerous as the females in this locality, while at Muillport 
Dr. Gemmill (5. p. 394) found that of about 250 limpets examined 
68 per cent were females. From some old observations by 
Lebert and Robin (6) it appears that in their experience there 
were about three males to eight or ten females, It would be 
interesting to discover the reason for this great variation in the 
proportion of the sexes. 
2. Growth Data. 
In order to study the rate of growth of the limpet throughout 
the year I marked a considerable number on December 31st, 
-1907, in a bay near the Cloch, Gourock, and attempted to keep 
full records of their growth from month to month during 1908. 
A number of them of course disappeared during the year, but 
their places were filled by others; for example on May 25th and 
May 30th, I measured about two dozen small-sized limpets and 
kept many of them under observation until the end of the year. 
The detailed records are given in Table I. where they are 
arranged in year-groups, and more or less in order of magnitude 
in each group. M = mean value. 
The possibility of arranging the measurements in year-groups, 
at least for the first two year's, arises from the fact that the 
breeding-season of the limpet, though a very long one, is fairly 
well-defined. 
Taste I.—Growth-Data, arranged in Year-Groups. 
1908 brood,Oct. 31, 11-5 mm. Nov. 30, 13 mm. 
Frrsr Year-Grovur (1907 brood). 
1907|1908 | | | | 
\Dec.|Jan.|Feb.|Mar. Apr.) May May|May June] July |Sep. Oct. | | Oct. Nov. Dee. 
SUS WEG, | Lan (ose) 5s a0) 27. |) 80: ari) ee soe 
| eee ee | F uw | —|— 
Tad oe (fox (OS VOR ees |e |G eka 
Pes) cea. 0 || \aa9! a4e5 | | | 
enoleEy 10-4) 11 | 19:5) 15°3) | .. | 189 | 19°8 | 23°7 26 27-6 
1 PG Gos ines ina 168 = ee ee 238 | 271 Bl elena 
5... 14) 12 | ... 164... | .. 20892626398 [o03) | 
Bhi | ae ies 9 Fire ae | 
his | fea ea) tay 20291 21 
eae ho. | lig |... 15 |171/20 |22 |23 apm 
9... be ne 119 149 | 182 | 208 225 Sdawillinies 
Teta Ba ee ard iowileemn | Nees lila 
