51 
distance from the parent rock (probably from north to south), and mixed with 
boulders of all kinds from the boulder clay which abounds on the land adjoining, 
and with pebbles from the glacial gravels and sands which cap the clay. 
“ Of the boundary lines shown, those exhibiting the undersea extension of 
the Great Whin Sill are the least doubtful, and that separating the Carboni- 
ferous from the Permian the least certain. 
“It must be clearly understood that, except as regards the Whin Sill, 
though the general relations and trend of the stratigraphical boundary lines are 
drawn with some confidence, their exact position is and must probably ever 
remain doubtful. 
“It inay be added that some miles seaward of the area depicted, a deposit of 
Tertiary beds of Pliocene (Crag) Age very probably overlies the older rocks un' 
conformably.” 
6.— LIFE HISTORIES. 
Statements have been made in previous reports as to what was 
known with regard to the life histories of the crab and lobster. It 
will be useful to present briefly the main facts. 
1. — Number of ova borne by the Female. — In the case of the 
American lobster, Herrick determined the number of ova borne by 
the female in 4,645 examples, measuring from 8 to 19 inches. The 
number varied from 3,045 to 97,440, the average for each size being 
4,822 to 77,647. Our lobster appears to be very similar and the 
number of ova borne by the berried female may therefore be said to 
be on the average about 40,000 — it being understood that the number 
of ova carried by the female increases with the size of the lobster. 
In the report for 1899 there was published an estimate of the 
number of ova on a berried crab, viz., about 1,000,000. Williamson 
found in 6 examples, varying from 5f to 7ii inches, that the number 
of ova was from about 460,000 to 8,000,000, and that in this case 
it was true also, the larger the crab the greater the number of ova. 
Other determinations have been made which show that it may be 
assumed that the berried crab carries on the average about 1,000,000 
ova. 
2. — Spawning Season. — Ehrenbaum found the spawning season 
of the lobster at Heligoland to be mid July to mid September. 
Fullarton’s observations proved that the season was much the same 
for Brodick. On our coast it is not likely to be much if at all 
different. Newly spawned lobsters have been found in July and 
August. 
The crab, as is now well known, spawns during the months 
November to January and possibly the beginning of February. 
