916 THE ANIMAL KINGDOM. 



character of the spores (flagellttlae and amoebnlae), the formation of 

 sporocysts or free chlamydospores, Zopf relegates the Monadineae to the 

 Mycetozoa as 'lower Mycetozoa.' But they are all distinctly animal in 

 their nutrition, with two exceptions, Haplococcus which lives between the 

 muscle-fibres of swine, &c., and Bursulla which flourishes in horse-dung. 

 Another difference, as compared with the Mycetozoa, is the fact, pointed 

 out by Zopf himself, that the higher Mycetozoa have nothing to cor- 

 respond to the zoocyst phase. As will be seen from the account given 

 below, our knowledge of some of the forms is very defective, and others do 

 not follow completely the typical life-history. 



There remain some Amoeboid organisms about which little is known, 

 differentiated from one another by shape, character of the pseudopodia, 

 mode of locomotion and of occurrence. Many of them, like some of the 

 forms of Heliozoon-aspect, are non-nucleate, or are said to be non-nucleate. 

 The latter were grouped together by Haeckel as Monera, but it is doubtful 

 how far the distinction, even if found to hold good, justifies such an 

 association 1 . 



The following epitome of the Proteomyxa is given principally for 

 the use of persons who may take an interest in these simple organisms. 



Heliozoon-like genera ; Nuclearia, Myxastrum, A rcherina, Monobia, Myxodyc- 

 tium. The first-named is freshwater, globular when in a state of rest, elongate and 

 somewhat lobed when in motion. Its pseudopodia are long, pointed and branched 

 at an acute angle, radiating or confined to a portion of the body when in motion. 

 It is frequently surrounded by a hyaline gelatinous layer beset with minute rods. 

 It has one or many nuclei, and a number of slowly contractile vacuoles. It lives 

 on A/ga-ce\\s, the contents of which it sucks out. A double cyst has been observed 

 in one of the two species. Myxastrum is marine ; it is globular with radiant pseudo- 

 podia, long, pointed, in one species sometimes branched at an acute angle, and 

 anastomosing. M. Liguricum is multinucleate, M. radians is said by Haeckel to be 

 non-nucleate. The latter forms a structureless membraneless cyst, within which the 

 protoplasm segments into a number of radially arranged oval spores. Each spore 

 acquires a siliceous investment, and gives exit to a minute Myxastrum. Archerina 

 is freshwater and non-nucleate. It is Acttnop/irys-like, and ^^ ^ of an inch in 

 diameter. It has motionless radiant pseudopodia, one or more non-contractile 

 vacuoles, and a bifid or double chlorophyl body. The chlorophyl body divides into 

 four and does so repeatedly ; at the same time the protoplasm increases in amount, 



1 The evidence for the complete absence of a nucleus rests in some instances on the authority of 

 observers, working with full command of the most modern histological methods, e. g. Ray Lankester 

 on Archerina, Gruber on Protamocba vorax. See also a paper by Brandt, ' Microchemische 

 Untersuchungen,' S.B. Physiol. Ges. Berlin, 1879. Gruber has pointed out that non-nucleate 

 parts of individuals may grow in size, heal a wound, carry on to complete development an organ 

 which has begun to develope, but they are incapable of starting the development of an organ and of 

 reproduction ; see Biol. Centralblatt. iii. p. 580, and A. N. H. (5), xvii. p. 482. But non-nucleate 

 organisms such as Archerina or Monobia are capable of reproduction. The cases are therefore not 

 parallel. 



