A proof that this substance is not really eggs is the fact that such 'eggs' are always found in some testacea, as in pinnae, trumpet shells, and purple fish; only they are sometimes larger and sometimes smaller; in others, as scallops, mussels, and the so called lagoon oysters, they are not always present but only in the spring; as the season advances they dwindle and at last disappear altogether; the reason being that the spring is favourable to their being in good condition.