cannot afford to liberate such a small number freely into the plankton. In my reading, I have been struck by how many of the smallest progenetic organisms, living in obvious r environments and possessing all other classical attributes of an r strategist, brood a few relatively large eggs. Neither Hoagland nor I are attacking the concept ofr and K strategies, but merely one of the criteria advanced for larger organisms and then extrapolated to smaller ones without adequate consideration of structural and energetic constraints. We must remember that lowered fecundity does not imply a smaller r if maturation is correspondingly accelerated. If, as Lewontin argued (1965), accelerated maturation is more effective than increased fecundity in raising r, then a progenetic trade of reduced fecundity for markedly accelerated maturation will provide an excellent r strategy for tiny animals. Harper (1967, pp. 255–256), in the quotation cited previously, noted the effect of a few precociously produced offspring in raising r.

To be effective in ecological time, heterochrony must be a potentially rapid response to changing conditions. Before testing my general hypothesis, I will discuss the most important data concerning potential ease and speed of heterochronic change.

The Potential Ease and Rapidity
of Heterochronic Change

The Control of Metamorphosis in Insects

If ontogeny includes a change in form sufficiently abrupt and substantial to warrant the term metamorphosis, then heterochronic effects can be easily diagnosed either by an alteration in timing of metamorphosis itself or by the differential acceleration and retardation of morphological traits with respect to metamorphosis. Moreover, the hormonal basis of several metamorphoses has been established (Jenkin, 1970) and heterochronies can be produced and replicated experimentally (though biologists have rarely discussed this experimental research in the context of relationships between ontogeny and phylogeny).

Although Willis (1974, p. 98) reminds us that "much of this scheme is still subject to controversy," the classical interpretation of hormonal control of metamorphosis in holometabolous insects involves the interaction of two substances. Molting is regulated by ecdysone (molting hormone), secreted by the pro thoracic glands. The morphological results of any molt, however, are determined by the juvenile hormone produced by the corpus allatum, an endocrine organ lying just behind the brain. This hormone has been synthesized and