1890-91.] Prof. MTntosh on Marine Food- Fishes. 
269 
involved in considerable confusion. Both forms have now been 
shown to have small demersal eggs which possess a single large 
coloured oil-globule when ripe, and, moreover, have the zona radiata 
covered by a special papillose layer which causes them to adhere 
to plates of glass and other foreign bodies. In the larger Sand- 
eel the oil-globule is greenish yellow, in the lesser it is reddish 
or brownish yellow. In the earlier stages of the eggs in the 
ovary, the particles of greenish yellow oil are scattered throughout 
the granular yolk, but they gradually coalesce until the mature 
ovarian egg has only a single large globule. Towards the period of 
hatching, these globules undergo a curious change of tint in the 
embryos, just before yellowish pigment appears in the trunk, and 
the special papillose coating of the egg disappears, leaving the zona 
bare. As in the herring, no vitelline circulation is established, and 
the yolk is considerably diminished before extrusion. The investi- 
gation of the developing eggs has also cleared up the relationships 
of certain larvse, such as D and G,* which are shown to be the early 
stages of the forms under consideration. They occur in great 
numbers at certain seasons, as in March. It was apparent that they 
did not spring from pelagic eggs, since these would have been 
captured by the various nets before the advent of the young forms. 
It is now evident that two spawning periods or a much prolonged 
one are characteristic of the Sand-eel, the larvse of which are found 
from March to July,, or perhaps even later. 
By the frequent use of various kinds of tow-nets on board the 
4 Garland ’ and at St Andrews, at all seasons, an endeavour has 
been made to ascertain the distribution of the pelagic eggs of the 
food-fishes round our shores. They have been found at all depths, 
surface, midwater, and bottom, and sometimes in great numbers, 
especially where cod, haddock, whiting, and other forms congregate. 
Their abundance, as formerly indicated, is generally in keeping with 
that of the adults in the neighbourhood, though many are swept 
into adjacent areas where few or no adults occur. Moreover, while 
there is a general resemblance in the collections of the pelagic ova 
of the British coasts, certain areas have features of their own. Thus, 
the floating eggs of the pilchard and mackerel are characteristic of 
the south and south-west ; the eastern waters of Scotland, as off the 
* Trans. Roy. Soc. Edin. , vol. xxxv. pt. iii. pp. 860, 861, plate viii. fig. 1. 
