ZOOLOGY 



The classification here adopted is taken from Lankester's 

 article on Protozoa. 



Class I. Proteomyxa. 



The simplest forms of Gymnomyxa are grouped together 

 in the class Proteomyxa. As an example of this class the life- 

 history of Protomyxa aurantiaca, a minute organism found in 

 1867 by Professor Haeekel, living on the coiled shells of the 

 MoUusc Spirula, in the Canary Isles, may be described. Many 

 of these shells were found bearing on their white surface a 

 minute globular mass of an orange - brown colour. Each 

 globule or cyst consisted of a central mass of protoplasm, 

 surrounded by a structureless membrane ; in the older cysts 

 the central protopksm appeared to be segmented into a num- 

 ber of parts, each of which, on the bursting of the membrane, 

 escaped in the form of a flagellula or pear-shaped swarm-spore. 

 These moved actively about by the lashing of their whip-like 

 pseudopodium, and soon underwent a change in form ; instead 

 of one pseudopodium which acted as a flagellum, they devel- 

 oped several, and then moved about like so many amoebae. 

 After creeping about for some time, these amoeboid organisms 

 fused together and formed a plasmodium, which in some cases 

 attained such a size as to be visible to the naked eye. The 

 Plasmodium gave rise to many branching ragged pseudopodia, 

 by whose aid it ingested great numbers of diatoms and other 

 food particles. It was much vacuolated, although none of the 

 vacuoles were contractile. After crawhng over the Spirula 

 shell for a time the plasmodium retracted its pseudopodia and 

 became spherical ; it then surrounded itself with a cell waU, and 

 the contents of the cyst thus formed broke up into flageUulae 

 in the way indicated above. No nucleus has yet been observed 

 in any phase of the life-history of this organism. 



Other genera have been described which live parasitically 

 upon Spirogyra ( Vampyrella spirogyrae) or Diatoms (Archerina 

 Boltoni, described by Lankester). In the latter chlorophyll 

 corpuscles are present, and seem to dominate the cell body 

 in a manner suggestive of a nucleus, which is otherwise 

 absent. 



