An introduction to the study of the comparative anatomy of animals . by an aggregation of denser proto-plasm. Eventually the nuclei, with the denser protoplasmaround them, become separated off as corpuscles, or sporo-blasts, and the remainder of the protoplasm of eachzygote disintegrates and disappears. Probably it goes toform reserve material. Each of the sporoblasts now sur-rounds itself with a lemon-shaped coat,* and becomes aspore of the kind commonly known as a pseudonavicella(fig. 32), from its supposed resemblance to a boat or nucleus of each spore now undergoes three successi
An introduction to the study of the comparative anatomy of animals . by an aggregation of denser proto-plasm. Eventually the nuclei, with the denser protoplasmaround them, become separated off as corpuscles, or sporo-blasts, and the remainder of the protoplasm of eachzygote disintegrates and disappears. Probably it goes toform reserve material. Each of the sporoblasts now sur-rounds itself with a lemon-shaped coat,* and becomes aspore of the kind commonly known as a pseudonavicella(fig. 32), from its supposed resemblance to a boat or nucleus of each spore now undergoes three successivenuclear divisions, giving rise to eight minute curved bodiesarranged round a central core of residual protoplasm, much * The chemical composition of this coat is not known. It is notsiliceous as was once supposed, nor does it appear to be chitinous. Digitized by Microsoft® MONOCYSTIS I5T as the divisions of an orange are arranged round the centralfibrous axis. These minute bodies, called the sporozoites,or sometimes the falciform { siCkle-shaped) young, are. Fig. 33-A, Conjugation of two zygotes of Monocystis agilis showing thenuclei and the partition wall between the zygotes. B,formation of the polar body, visible in one of the zygotesonly. C, approximation of the nuclei of the two zygotesafter formation of the polar bodies. D, two zygotesshowing division of the nuclei derived from the combinationnucleus. S, Two zygotes surrounded by a capsule. F, apseudonavicella containing eight sporozoites. (AfterWolters.) liberated, and enter the sperm-mother cells of the same, oranother, earthworm; but their actual history at this stagehas not been traced. It is probable that, after rupture of thecyst-wall, the sporozoites escape by bursting out of the Digitized by Microsoft® 158 COMPARATIVE ANATOMY pseudonavicella; that some of them make their way into the,sperm-mother cells of their host; whilst others are passed,to the exterior by the seminal ducts, and remain alive for a,while
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