236 MR. E. 8. RUSSELL ON THE SHELL-GROWTH [Mar. 2, 
small proportion of 10-15 mm. shells and on January 25th there 
was seemingly a greater proportion of small shells 7-10 mm. in 
length. After that I have no records which indicate the settling 
down of very young limpets until July 21st, when I found that 
the small shells were mostly 15-25 mm. in length (and therefore 
simply the descendants of the 10-15 mm. long limpets of 
January), but that an occasional small one (8 mm.) occurred 
among them. 
On August 4th at Millport I collected one or two tiny shells 
2°5-3 mm. long from the crevices of a rock in the lower half of 
the beach. On September 2nd at the Cloch, Gourock, there were 
visible in the bay a few 5-10 mm. shells, and on October Ist there 
were a few shells 8-12 mm. in length in places where they were 
not present on September 2nd. 
From these data it would appear that the breeding-season ex- 
tends from July to December or January. I examined also the 
gonad of a number of limpets at various times during the year. 
On September 18th, 1907, three limpets were examined. ‘Two 
of them were females, 28 mm. and 40 mm. in length, and the 
ovaries contained large but not quite ripe ova. In the 40 mm. 
long male the sper matozoa were fairly ripe. A number collected 
at the Cloch on December 25th, 1906, were quite ripe. Of 26 
limpets collected at Cardwell Bay, Gouroek, on December 28th 
and 31st, 1907, 21 were males and only 5 were females. The 
males were not very ripe and some of them seemed spent, 
but the females had mature sexual products. Of five males 
collected at the Cloch on January 11th, 1908, only one was at all 
ripe, the others being spent. Ten limpets, 4 females and 6 males, 
were taken on February 8th. The males seemed spent and the 
ova in the gonads of the females were disintegrating. The 
breeding season is clearly over by the end of January if not a 
little sooner. 
The sex of six limpets of 35-42 mm. in length collected on 
the 23rd May could not be determined with certainty, though 
they appeared to be males. The gonad was brick-red and only 
one-half to three-quarters its full size. At the anterior end it 
was beginning to turn cream-coloured, as if it were ripening into 
a-mature testis in that region. 
A male examined at Kames on July 2nd, 1906, had well- 
developed spermatozoa. 
On July 11th, eleven limpets were examined. Six of them 
were females and their ovaries were at all stages of ripeness. One 
or two showed a number of fairly ripe ova, and the ovar y had the 
typical olive-green tint which it shows when at all mature. The 
others were “extremely unripe with very minute ova, and the 
colour of the ovary was a reddish-brown. The males were all 
moderately ripe. J attempted to carry out artificial fertilisation, 
and rather to my surprise obtained a number of early segmen- 
tation stages. 
Artificial fertilisation was carried out with success at Mullport 
on August 4th, early segmentation stages being again obtained. 
