THE S ARC ODIN A 95 



of the shells which Munier-Chalmas ('83) and Schlumberger ('83) 

 have shown to be widespread throughout the group. The original 

 nucleus divides into numerous parts, which are spread throughout all 

 of the chambers. The protoplasm then segregates about them, and 

 the original mass of plasm becomes divided into as many parts as there 

 are nuclei. These leave the parent organism either by rupture of 

 the shell or through the mouth-opening, and soon form new shells 

 (megalospheric). After a short time they bud, and calcium car- 

 bonate is secreted around the bud, thus making a two-chambered cell. 

 This process continues until the organism is full grown. Finally, the 

 pseudopodia are drawn into the shell, and the protoplasm divides 

 into numerous small swarm-spores, each with two flagella. These 

 probably conjugate (Lister, '95 ; Schaudinn, '95), the copula giving 

 rise to individuals with shells of the microspheric form. A very 

 similar process occurs in the Radiolaria, where the endoplasm within 

 the central capsule breaks up into swarm-spores, each with a portion 

 of the original nucleus and each provided with flagella. These finally 

 break out of the capsule, and, after a short free-swimming period, they 

 lose their flagella and gradually assume the typical radiolarian form, 

 passing through Heliozoa stages. In some cases, dimorphic spores 

 (anisospores) are formed, which perhaps conjugate, as assumed by 

 Brandt ('85) and Haeckel ('88), although the process has never been 

 seen. Here, too, an alternation of generations is assumed by Haeckel 

 and Brandt, an asexual or iso spore generation alternating with a sexual 

 anispore generation. 



In addition to simple division and swarm-spore formation, some 

 Sarcodina reproduce by bud-formation or gemmation. Buck ('77) 

 early observed a number of small amoeboid germs in the shell of 

 Arcella (as many as thirty), an observation since confirmed by Cat- 

 taneo ('78), Biitschli, and recently by Hertwig ('99). Both Buck and 

 Cattaneo traced the development of the buds up to the formation 

 of the characteristic shell, while Hertwig has described the nuclear 

 divisions leading to bud-formation. Butschli found that the number 

 of amoeboid buds does not exceed nine. Le Blanc ('92) describes 

 similar processes in Difflugia. Somewhat similar buds were observed 

 inside Pelomyxa palustris by Weldon, 1 although neither the devel- 

 opment nor origin was made out. Bud-formation has been repeatedly 

 seen in the Heliozoa as well as in the Rhizopoda. The genus Acan- 

 thocystis in particular has been studied in this connection by Hertwig 

 ('74), Korotneff, and more recently by Schaudinn ('96). According 

 to the latter, the nucleus divides by amitosis, the daughter-nuclei 

 moving toward the periphery, where they bud off with a small amount 

 of cytoplasm ; in some cases as many as twenty-four buds may be 



J Cf. Lankester ('91). 



