12 Part 111 —Twenty-first Annual Report 
Megalops, which is a connecting link between the pelagic Zoéa and 
the demersal young crab, which lives on the bottom, partaking of 
the character of both, being adapted either for swimming or 
crawling, and this finally gives rise to the young crab. 
With reference to growth, it was found that a considerable 
amount of variation occurred, due to the fact that increase in size 
only takes place after a moult, and the amount of the increase 
varies not only with the individual, but also in the same specimen 
in different moults. It is, however, possible with a fair amount of 
certainty to separate the crabs into yearly groups if attention be 
given, in the case of small crabs, to the month in which they are 
captured. Observations have also been made on the amount of 
erowth that takes place in successive moults of specimens kept in 
confinement; and Dr. Williamson’s observations in this respect 
were supplemented by a valuable series of cast shells from Mr. 
H. T. Waddington, Bournemonth. The conclusions reached are 
that the shore crab, when one year old, may measure from about 
one-third of an inch to nine-tenths of an inch in breadth, the 
average being a little over half-an-inch. When two years old the 
average breadth of the male is about two inches, and of the female 
nearly one inch and three-fifths; when three years of age the male 
is about two-and-two-fifths of an inch broad, and the female about 
one-fifth of an inch less. The number of moults in a year was 
found to vary considerably. 
THE INVERTEBRATE FAUNA. 
The collections of crustacea which have been made in the course 
of the fishing investigations have proved of considerable interest, 
and in the present Report Dr. Thomas Scott contributes a further 
paper dealing more particularly with the Copepoda. These minute 
forms play an important réle in connection with the food of fishes. 
They exist in enormous multitudes and constitute one of the chief 
agencies by which the primary source of food, namely plant- 
organisms, is transformed and rendered available for the nutrition 
of fishes. Many fishes, as the herring and the sprat, the anchovy, 
the mackerel, and the pilchard or sardine, subsist mainly upon 
copepoda, while almost all other fishes live upon them in their young 
and early stages. 
In the present paper Dr. Scott describes a large number of species, 
of which thirteen, belonging to eight genera, are new to science, 
the descriptions being illustrated by a series of drawings. In some 
instances the determination of these minute forms is of importance 
for other reasons, as in tracing the course of sea-currents. Thus, 
for example, one species which is described, Hucalanus crassus, was 
obtained about ten miles off Aberdeen, and was previously recorded 
from the Moray Firth, from the region south-east of Fair Isle, and 
from the Farde Channel. Its distribution is known to extend as far 
south as the Gulf of Guinea, and its appearance in the Moray Firth 
and off the East Coast probably indicates the presence of Atlantic 
water. It is interesting t> note that all the specimens were taken 
in October and November. 
