so 



Structure and Classification of Micro-organisms 



Rhizopoda, h^t in the corticata there may not only be a permanent 

 form, but there may be adaptations, such as an oral aperture, some- 

 times infundibular in shape and communicating with the soft 

 endosarc through a blind tube. An anal aperture, may also be 

 present. 



In the higher infusoria the ectosarc may also be continued pos- 

 teriorly to form a stalk, by which the organism attaches itself 

 (VorticeUa). Such stalks are contractile. 



Nucleus.— In certain protozoa of very simple and indefinite 

 structure— Spirochseta and Treponema— no distinct well-contoured 

 nucleus can be observed. 



In the rhizopoda the nucleus is a distinct organ surrounded by a 

 nuclear membrane and containing the usual chromatin and linin. 



Fig. 17. — Internal parasites: A, Amceba coli, Losch; B, Monocystis agilis, 

 Leuck., a gregarine; C, Megastoma entericum, Grassi, a flagellate; D, Balantidium 

 colli Ehr., a ciliate. Under very different magnifications. 



The greater number of Mastigophora possess two distinct bodies, 

 either a nucleus and a centrosome or a major and' minor nucleus. 

 This is well shown in Trypanosoma. 



The infusoria vary. greatly in the character of the nuclei. As 

 a rule, there are two indefinite nuclei, the macronucleus and the 

 micronucleus. Both seem to be essential organs, and in the phe- 

 nomena supervening upon conjugation both participate. The nuc- 

 lei of the protozoa are, therefore, extremely diversified, and vary 

 from the most simple collections of granules of nuclear substance 

 to large well-formed fantastically shaped composite organs. 



Movement. — Some kind of movement is to be observed at some 

 period in the life of almost every protozoan. 



In Rhizopoda with the soft ectosarc the movement consists of 

 flowing currents by which lobose projections of the body substance 

 appear now here, now there, in the form of pseudopodia, or else a 

 continuous flowing, by which the upper surface continually coming 



