LACK OF CORRELATION OF SOME PROECDYSIAL GROWTH AND DEVELOPMENTAL PROCESSES IN THE CRAYFISH

¹ Department of Biological Sciences, Kent State University, Kent, Ohio 44240

1. New setae can be seen in the process of development in the uropods and telson of living specimens of Orconectes sanborni. The setae form by secretion of a tube within a tube. Three stages in the formation of the new setae can be used to subdivide intermolt stage D₁ into three substages.

2. The beginning of seta formation defines the beginning of stage D₁. Before beginning this stage, the membranous layer of the cuticle begins to be reabsorbed the epidermis separates from the old cuticle, gastroliths begin to be formed, and the rate of regenerating limb growth increases sharply except in individuals which do not display such increase at all.

3. The membranous layer had been completely reabsorbed in about half the specimens examined in each D₁ substage. Therefore, the rate of reabsorption of the membranous layer is not correlated with the rate of seta formation.

4. Ratios of gastrolith length to carapace length and of regenerating limb bud length to carapace length varied in different specimens, but the variations were not correlated either with D₁ substage and therefore with rate of seta formation or with reabsorption of the membranous layer.

5. Growth curves of regenerating limb buds followed seven different patterns.

6. Mean lengths of premolt stages of animals of 1.5 to 3.4 cm. carapace length were: stage D₁', 5.3 days; stage D₁'', 3.3 days; stage D₁[unknown] and stage D₂ together, 2.4 days; stage D₃, 3.0 days.