31 



Write a short Account of the Mode of Reproduction in Actino- 

 sphcerium. 



Asexual reproduction by binary fission is the normal 

 method ; but there is also a sexual process, the chief 

 phases of which are as follows: The individual with- 

 draws its pseudopodia, the non-contractile vacuoles dis- 

 appear, and it sinks to the bottom of the pond, becomes 

 amoeboid, and soon encloses itself in a soft cyst. Food 

 reserves called " yolk-plates " are formed, and simul- 

 taneously the number of nuclei is greatly reduced. The 

 body then divides up. Each segment has a nucleus and 

 is enclosed in a siliceous " primary cyst." Each primary 

 oyst divides into two " secondary cysts," and these become 

 gametoctyes which undergo nuclear division and extrude 

 polar bodies. The two cells behave like gametes, they 

 conjugate and form a zygote which is the spore. Its nu- 

 oleus undergoes mitotic division, and the spore then emer- 

 ges from the cyst as a young Actinosphcerium with several 

 nuclei. 



CLASS FORAMINIFERA, 



What are the Special Features of the Foraminifera ? State 

 where they are found and give Examples. 



The protoplasm is uniform (not differentiated into 

 ectoplasm and endoplasm). The viscid pseudopodia are 

 long and thread-like, branch freely, and often anastomose 

 to form networks ; they serve for attachment as well as 

 for locomotion and for securing food. 



A test or shell, usually limy and chambered, is secreted 

 by the protoplasm. In certain forms the shell has one 

 or more large apertures ; in most it is also perforated with 

 numerous minute holes (hence the name Foraminifera). 

 The protoplasm may pass out from the large apertures 

 {e.g., Gromia), or through the numerous perforations, and 

 form a thin layer covering the shell ; from this layer 

 pseudopodia are given off (e.g., Polystomella). 



There is either one nucleus or many. The multinucleate 



