It has long been customary to attempt the solution of some of the problems of protoplasm and the physiologic riddles of life by means of observations on lower organisms and simpler forms. The unicellular animals have afforded particularly useful and easily available objects for investigation from this point of view. Their supposedly simpler structure and more diffuse phenomena seem to render them particularly suitable to elucidate the more general properties of living matter. Among other questions, the problems of protoplasmic senescence and the significance of fertilization have seemed open to direct investigation in this field. In certain of the Infusoria, for example, reproduction proceeds by unprovoked cell division; but the frequent occurrence of conjugation, in all of the species, affords an instance of what may be looked on as the counterpart of fertilization in the higher forms.
Is conjugation an indispensable activity for the prolonged generation of these lower organisms?