284 Mr. A. T. Masterman on the Life-history 
measured specimens, grouped according to the months; and, 
without going further, it is evident that there is a series of 
larval sand-eels found in March and April, and another 
series, in lesser numbers, in the end of July ‘and August. 
The enormous quantities of larvee which suddenly make their 
appearance in March at the sandy bottom some way from 
shore show a gradation in size, the smallest being 3°8 to 4 
millim. (in spirit); and, by the presence of an oil-globule 
-and traces of yolk, they must have just reached the end of the 
larval period. The period of hatching is in the summer about 
ten days, so that a period of incubation of three weeks would 
not be excessive for the mid-winter time (see my remarks on 
plaice). The larval period will also be considerably prolonged. 
For the summer larva a more or less quiescent larval period 
of two weeks would not be abnormal from the analogy of other 
species, and this is probably understating the case. This will 
give us a larval period of four weeks in the winter at least, 
and therefore we may say that the larve found in early 
March were probably spawned at the end of the year (incu- 
bation three weeks, larval period four or five weeks). This 
date would agree with the observations of Couch, quoted 
above, on the date of spawning. We know that the sand-eel 
lays its eggs ¢n the sand, and it would not be a great assump- 
tion to suppose that the newly-hatched larve avail them- 
selves of the protection afforded by their surroundings to 
remain in the sand until, the yolk being nearly absorbed, they 
emerge from their concealment and suddenly appear in count- 
less numbers upon the sandy bottom. There are facts to 
hand which point to the conclusion that some young littoral 
pleuronectids (plaice &c.) take refuge during the winter 
months by embedding themselves in the sand. (On this 
point see also Petersen, ‘ Report Danish Biol. Stat.,’ 1893.) 
Although there is a certain amount of hypothesis in this 
account, yet it must be said that it agrees exactly with the 
facts at present known, and no other theory has yet ful- 
filled these conditions. Fullarton has put forward the 
suggestion that the little March larve are trom the previous 
summer’s spawning :—“ Those captured in March, April, and 
May .... may beconsidered as having been hatched towards 
the latter part of the previous spawning-period.” This 
assumption would require that these little larve with oil- 
globules and, in some cases, traces of yolk, many not exceeding 
in size the just-hatched summer forms, must be at least seven 
months old, the first three of which are the hottest and best 
growing months of the year. This difficulty is got over by 
assuming that the spawning-period extends from “ June till 
