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form A, and the form with the small primordial cltamber 

 (microspheric) form B. Working with Schlumberger, he found 

 that many other genera and species showed the same difference 

 in the size of the primordial chamber, and that this difference 

 of size was often associated with differences in the method of 

 arrangement of the early chambers. The investigation of this 

 phenomenon has now been carried out in the living organism, 

 chiefly by Schaudinn in Germany, and J. J. Lister in this 

 country, and it has thrown much light on the method of repro- 

 duction in the Foraminifera. The main point of difference between 

 the living megalospheric and microspheric forams is found in the 

 character of the nucleus. The megalospheric type has in its 

 early stages but a single large nucleus, while the microspheric 

 type is multi-nucleate. The method of reproduction in the two 

 forms depends on this character, and is as follows : In the micro- 

 spheric and multi-nucleate type the protoplasm emerges from 

 the shell and collects in a ring of minute globules outside, each 

 globule forming round one of the nuclei. According to Lister, 

 as many as 200 of these globules are simultaneously formed, each 

 of which secretes a shell which is always of the opposite type 

 to the parent — i.e. a megalospheric type. The parent then dies, 

 and the young brood disperse. Following up the life-history of 

 these megalospheric young shells, which, during the greater part 

 of their life, possess only the single nucleus derived from the 

 parent, it is found that after a time the nucleus disappears, and 

 is replaced by innumerable micro-nuclei. Each of these segre- 

 gates a particle of protoplasm, and, after repeated subdivisions, 

 the whole of the protoplasm breaks up into a mass of binagellate 

 spores. What became of these spores was for many years in 

 doubt ; but a few years ago Schaudinn observed the conjugation 

 of two spores, and watched the subsequent growth of a microspheric 

 shell. The origin of the microspheric shell, which had long been 

 a mystery, was thus solved, and proved to be the result of a 

 sexual process. Dimorphism has now been observed in a great 

 many genera and species, but it would not be safe to say that all 

 Foraminifera are dimorphic, although this probably is the case. 

 The difference in the sizes of the primordial chambers varies very 

 much in the species observed. In Biloculina they are about as 

 15 to 1, but in some others the difference is slight. The size 

 of the adult shell may be very different in the two forms, as in 



