1893.] IJJ [Ryder. 



vai-ious forms of the facets of the compound eyes of insects arisen. So 

 too the reciprocal marginal interference of the growth at six equidistant 

 points of the scutes of such forms as the extinct Glyptodonts, has devel- 

 oped in sucli scutes a hexagonal configuration. In these cases growth is 

 the kinetogenetic factor, and the statogenetic factor is the struggle to 

 bring about an equilibrium of marginal pressures during growth, as a 

 consequence of which a hexagonal figure results. 



The development of a cylindrical form of the body is also a case where 

 an equilibrium is concerned that is largely statical in character. The 

 tense condition of its fluid-containing cavities, such as the alimentary 

 canal, will confer upon such an organ a cylindrical configuration ; so also 

 in the case of blood vessels. It is indeed probable that the very form of 

 the blood corpuscles or disks is discoidal in virtue of a statical equilibrium 

 of their substance within the fluid plasma in which they are immersed, 

 and that there is a double vortical flux of the substance of these disks 

 from the centre to the periphery on both faces, or the reverse. This vor- 

 tical flux is probably maintained by the exigencies of metabolism and calls 

 for the incessant exhibition of a tendency tow^ards a condition of statical 

 equilibrium. In this way we may conceive that the thousands of millions 

 of red blood disks coursing through our vessels are enabled to not only 

 maintain their flattened configurations, but to also thus greatly increase 

 the areas of their surfaces and be thus rendered more efflcient agents in 

 the processes of oxidation and deoxidation. Here is a statical condition, 

 as we may suppose, that has been adaplively developed through tiie 

 direct expenditure of energy, by the matter of the corpuscle itself. In 

 other words, our red blood corpuscles have, in the first place, and with 

 llie utmost probabilitj', acquired their present configuration ergogenetic- 

 ally. If this is true in the case of the blood disks of ourselves, it is prob- 

 ably also true of the blood disks of all other forms. 



The globular form of the egg is a statically developed condition, so is 

 that of the more or less nearly globular morula and also of the blastula; 

 but in the latter internal osmotic pressure is also a factor. Even the brain 

 shows in its earliest form the tendency to develop as vesicles under stat- 

 ical conditions. Here its growth is the kinetogenetic factor, and the ten- 

 dency for the hemispheres to be at first globular vesicles is owing to the 

 statical influence of the substance composing their walls. Later, as these 

 vesicles grow, they press upon each other along the median line when they 

 present a flattened aspect towards one another from the operation of the 

 same causes, and we at last have developed the "hemispheres" of anato- 

 mists. In this way it results that a single somewhat globular body is 

 formed, made up of two halves. Under constraint within the membranous 

 cranial walls the latter conform to this pressure of the growing brain- 

 globe within and conform to its shape, so that a somewhat globular cra- 

 nium results. Following in detail the evolution of the fissures of the brain, 

 even these are developed kinetogenetically through growth ; the pallium 

 or cortex under restraint within the skull grows and shows a tendency to 



PROC. AMER. PHILOS. SOC. XXXI. 141. Z. PRINTED JUNE 30, 1893. 



