Shell-fish industries . d ova of the simplest and the most highly special-ized of many-celled animals, we are able to discoveronly minor differences in structure, such as are easily ac-counted for by secondary causes—a greater or less ac-cumulation of yolk and the like. Even the fertilizedova of plants are essentially similar to these. And yetwe know that each holds in its minute body, when living,the hidden power to set in motion and to continue a longseries of marvelous transformations, ending in one casein the production of a sponge, or in another of a humanbeing. The marvel of it was recog
Shell-fish industries . d ova of the simplest and the most highly special-ized of many-celled animals, we are able to discoveronly minor differences in structure, such as are easily ac-counted for by secondary causes—a greater or less ac-cumulation of yolk and the like. Even the fertilizedova of plants are essentially similar to these. And yetwe know that each holds in its minute body, when living,the hidden power to set in motion and to continue a longseries of marvelous transformations, ending in one casein the production of a sponge, or in another of a humanbeing. The marvel of it was recognized before Paley, acentury ago, wrote:— A particle, in many cases minuterthan all assignable, all conceivable dimensions; an aura,an effluvium, an infinitesimal; determines the organiza-tion of a future body; does no less than fix whetherthat which is about to be produced, shall be a vegetable,a mere sentient, or a rational being: an oak, a frog,or a philosopher. The oosperm possesses the power of self-division, a. Fit;, ii. The development of the American oyster, afterProfessor W. K. Brooks. Development 45 power that its cell descendants retain. The man-ner of its division or segmentation in the Americanoyster will illustrate the process in the group of the bi-valves, and, briefly following the description of Pro-fcosor Brooks, is as follows:— About an hour after the male cell has entered theovum, the latter becomes somewhat enlarged at one end—that to which the pole cells are attached. The nucleusof the ovum divides, the two nuclei separate, and a con-striction of the body of the cell separates it into two cell to which the pole cells are attached soon di-vides, and a stage represented by II in Figure 11 are shown one large and two slightly smaller every division, there is a division of thenucleus, so that every cell always contains a nuclearbody. Even thus early in development, it is possible to de-termine a difference in the
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