326 BIOLOGY OF THE PROTOZOA 



plant cells thus making holes through which they enter the cells. 

 Products of chlorophyll nutrition frequently form reddish-colored 

 masses (karotin) in their protoplasm. Encystment, with cellulose 

 cyst walls is common. Nuclei are multiple as a rule; reproduction 

 by plasmotomy or by division into uninucleate amoebse ; flagellated 

 swarmers unknown. Accepted genera: NucJearia, Cienkowsky; 

 Arachnula, Cienkowsky, and VampyreJln, Cienkowsky (Fig. 145). 



Sub-class II. MYCETOZOA, de Bary. 



The Mycetozoa were formerly regarded as low types of fungi and 

 under the name of Myxomycetes or "slime moulds" were included 

 amongst the lower plants. The investigations of de Bary, however, 

 revealed the rhizopod affinities and the relationship with other 

 Sarcodina is now clearly recognized. There is little doubt, how- 

 ever, that Mycetozoa are borderline organisms and their semiterres- 

 trial habitat leads to modifications and adaptations not met with 

 elsewhere. Many of them are highly complex both as to organiza- 

 tion and as to life history and by no stretch of the imagination can 

 they be regarded as simple organisms. 



A general idea of the essential characteristics of the M3 cetozoa 

 may be gained by following through a typical life history beginning 

 with, a recently germinated "spore." This is a small uninucleate 

 amoeboid organism known as a "myxamoeba;" it is active, throwing 

 out pseudopodia and moving energetically about the field. It has 

 a contractile vacuole, and takes in solid food which is digested in a 

 gastric vacuole, or it may live upon dissolved proteins from decom- 

 posing organic matter. It may also reproduce by division while 

 in this amoeboid condition. 



The naked amoeboid condition is usually temporary; sooner or 

 later the "myxamoeba" turns into a "myxofiagellate" by the devel- 

 opment of a flagellum. The contractile vacuole is retained and the 

 body, usually ellipsoidal, is highly metabolic and may even give 

 rise to pseudopodia, particularly at the posterior end where the 

 pseudopodia aid in the ingestion of solid food in the form of bacteria, 

 small Protozoa or bits of organic detritus; saprozoic nutrition, how- 

 ever, is also common. Like the "nnxamoebse" the "myxoflagel- 

 lates" may reproduce by longitudinal division, in which case the 

 centrioies of the mitotic figure become the basal bodies of the 

 flagella. Myxoflagellates are apparently rather sensitive and show 

 a ready tendency to encyst. Such "microcysts" are temporary 

 and the excysted organism again passes through myxamoeba and 

 myxofiagellate stages. 



According to later investigations of Jahn these myxofiagellates 

 ultimately become gametes; the last division, prior to gamete 

 formation is a chromosome reducing division, and the haploid 



