Dec, 1908.] THE VICTORIAN NATURALIST. 123 



This took the form of a lecture in explanation of a fine series 

 of lantern illustrations, in which the more salient points regarding 

 our present knowledge of the life-history of this lowly but im- 

 portant group of organisms were dealt with. The Foraminifera, 

 not long since regarded as having a body of almost structureless 

 protoplasm, have been shown, by the careful studies of workers 

 like Williamson, Max Schultze, Alunier Chalmas, Schaudinn, and 

 Lister, to exhibit a wonderfully beautiful series of changes during 

 their existence, chiefly connected with their reproduction. Each 

 type-form is fitted to reproduce its kind in two ways — first, by 

 asexual division ; second, by the formation and conjugation of 

 zoospores. In the first case the resultant form commences with 

 a large chamber (form A) ; in the second, with a small chamber 

 (form B). From observation it is known that form A can give 

 rise either to form A or form B, but form B can only reproduce 

 the form A. The latter is characterized by a single nucleus, 

 excepting during the phase of reproduction, when the nucleus 

 divides by simple fission, and the resulting nuclei, each taking up 

 a thick coating of cytoplasm, is invested with a shelly covering, 

 breaking away as a separate entity of the megalospheric type. 

 Usually this reproduction is carried on in the multiloculine forms 

 in the peripheral chambers, which are known as '•' brood 

 chambers." In a similar manner megalospheric young are 

 reproduced by form B. The formation of microspheric young, 

 on the other hand, is carried out in the following way : — The 

 nucleus of form A disintegrates, the chromidia derived from the 

 nucleus create numerous little centres, each with a covering of 

 cytoplasm. These vesicular nuclei then divide twice by the 

 method of karyokinesis or mitosis, the resulting four cells being 

 each furnished with two flagellse. They thereupon conjugate with 

 other swarmers outside the shell. The fusion of their nuclei takes 

 place after some delay, and, lastly, the nucleus of the conjugated 

 body divides, and a shell is then formed. This constitutes the 

 microsphere. The phenomenon of "dimorphism" was first 

 suspected to indicate different reproductive stages of the same 

 species by Munier Chalmas, in regard to the coin-like Foraminifera 

 of Eocene age known as Nummulites. Earlier observers, how- 

 ever, as de la Harpe, von Hantken, and Rupert Jones, were well 

 aware of the existence of " couples " of Nummulites, in which one 

 of the forms had a large central chamber and a small test, whilst 

 the other had a small central chamber and a large test. Schlum- 

 berger, working in conjunction with Munier Chalmas, and later 

 by himself, was able to prove, by means of skilful section-cutting 

 of the tiny shells, the existence of dimorphism in practically all 

 the genera of the Miliolidse. There was one exception, however, 

 in the genus Alveolina, about which there was only a provisional 

 record of the occurrence of Form B (with the microsphere), by 



