. The cell; outlines of general anatomy and physiology. especially interesting and important in theconsideration of the problem in question, since some of the variousspecies, which in their whole appearance are extremely similar{Pandorina morum, Eudorina elegans, Volvox globator), exhibitmarked differences in their sexual cells, whilst others show nodifference at all, and in yet others an intermediate stage can beobserved. The whole relationship is so clearly demonstratedthat it is worth while to consider it more in detail. Pandorina morum, which is especially well known—for as earlyas 1869 Pr
. The cell; outlines of general anatomy and physiology. especially interesting and important in theconsideration of the problem in question, since some of the variousspecies, which in their whole appearance are extremely similar{Pandorina morum, Eudorina elegans, Volvox globator), exhibitmarked differences in their sexual cells, whilst others show nodifference at all, and in yet others an intermediate stage can beobserved. The whole relationship is so clearly demonstratedthat it is worth while to consider it more in detail. Pandorina morum, which is especially well known—for as earlyas 1869 Pringsheim (VII. 35) discovered the pairing of itsswarm-spores—forms small colonies of about sixteen cells, whichare enclosed in a common gelatinous sheath (Fig. 157 II). Eachcell bears two flagella on its anterior end ; these stretch outbeyond the surface of the gelatinous sheath, and are used forlocomotion. During sexual reproduction each of the sixteen cells splits upgenerally into eight portions, which aftar a time are set free, and 283 THE CELL. Fig. 157.—Development of Pandorina morum (after Pringsheim ; from Sachs, Fig. 411):/ a swarming family; If a similar family, divided into sixteen daughter-families; III asexual family, the individual cells of which are escaping the gelatinous investment; IV,V conjugation of pairs of swarmers; VI a zygote, which has just been completed ; VIIa fully grown zygote; VIII transformation of the contents of a zygote into a large swarm-cell ; IX the same after being set free ; X a young family developed from the latter. swim about independently (Fig. 157 III, IV). These swarm-cells, which are oval, and (with the exception of the anterior,somewhat pointed, hyaline end) are green in colour, possess a redpigment spot and two flagella ; they are somewhat unequal insize. However, in this respect a marked sexual differentiationis not apparent in Pandorina. For when swarm-cells from twodifferent colonies approach each other, it is seen amongst
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