115 



It now became the task of the investigators to watch the evolu- 

 tion of the megalospheric form. A considerable proportion of the 

 nucleoid bodies that during the embryonic condition were scat- 

 tered through the protoplasm of the microspherical individual 

 were seen to unite and form a compact mass, which became the 

 nucleus of a new megalospheric individual, and, according to 

 Lister, such nucleus generally occupies the primordial chamber. 

 When this individual of the megalospherical plan of growth has 

 reached the reproductive stage, the principal nucleus disappears, 

 broken up and absorbed into the protoplasmic mass, and minute 

 nuclei make their appearance. A karyokinetic division of all the 

 nuclei follows, the latter acting as centres around which the 

 protoplasm arranges itself, forming small spherical masses which 

 gradually and uniformly become distributed throughout the 

 protoplasmic body until the whole of the body substance is used 

 up in their formation, and the minute spheroids, which are the 

 ultimate product of this extended process of division, are set free 

 as flagellated zoospores of uniform size. These zoospores form 

 the embryos of the microspheric form of Polystomella crispa. 



In these results the biological significance of the megalospheric 

 and microspheric plans of growth among the Foraminifera has 

 been explained. It has been demonstrated there are two methods 

 of reproduction — one by the production of embryos, and the other 

 by the emission of spores. The microspherical group produce 

 young in the form of embryos, which develop into megalospheric 

 individuals; and the megalospherical group produce spores, which 

 in turn reproduce the species on the microspherical plan of 

 growth. In a few rare cases, however (Schaudinn noticed three 

 in 4,300), it has been observed that where no principal nucleus 

 was formed in a megalospherical individual, the small nucleoid 

 bodies multiply directly from themselves, forming embryos instead 

 of spores. In this case a megalospherical parent produces 

 megalospheric offspring without an intermediate microspheric 

 generation. The proportion of numbers in the two forms is 

 worthy of note. The megalospheric form is much more common 

 than the microspheric. The proportion in Polystomella crispa, 

 according to Lister, is in the ratio of 34 to 1 ; and in Adelosina 

 polygonia, according to Schlumberger, the relative proportions 

 are as 8 to 1. The season of the year has apparently something 

 to do with these relative numbers, for the microspheric, or spore- 

 produced forms, on Lister's observations, occur in greater numbers 

 in the height of summer than in other parts of the year. 



If I may for a moment longer tax your patience in reviewing 

 these biological researches I would refer to a recent discovery in 

 which M. Schaudinn has still further advanced our knowledge of 

 the life history of the Foraminifera. He has obtained abundant 



