THE MYXOMYCETES OR MYCETOZOA ; ANIMALS OR PLANTS ? 113 
simplest expression, takes place with the Myxogasters, or as 
they may he preferably designated the Mycetozoa, this last- 
named group can undoubtedly claim bonds of affinity with 
other more complex Protozoa. Thus, as previously intimated, 
the horny rete or capillitium mostly, hut not always,, developed 
within the sporangium of the Mycetozoa, singularly resembles the 
horny network or skeletal elements of the keratose sponges ; 
while the calcareous concretions also frequently, but not in- 
variably, developed in intimate connexion with the capillitium 
and wall of the sporangium, may be similarly compared with 
the mineral concretions or spicula of the sponges. As certain 
sponges occur that possess neither a horny rete nor spicula, so 
Mycetozoa are also to be found having; no mineral concretions, 
and in which the capillitium is either absent or altogether 
rudimentary, demonstrating alike in either instance the non- 
essentiality of these several elements. A case in point illus- 
trative of the resemblance that subsists- between sponge spicules 
and the mineral concretions of the so-called Fungi is afforded by 
the species of Physarum, whose developmental phenomena have 
just been recounted, and in which, as shown at PI. IV., fig. 
35, the minute stellate calcareous bodies scattered over the 
outer wall of the sporangium, are directly comparable with the 
minute stellate spicula characteristic of the Sponge group dis- 
tinguished by the title of the Tethyidse.* In yet another direc- 
tion the two groups of the Mycetozoa and Spongida may be 
co-ordinated. The sporangia or spore-receptacles of the first- 
named class, representing the quiescent state entered upon as the 
closing act of vegetative life, while morphologically comparable 
with the encysted phases of the ordinary Flagellate Infusoria, 
may, in virtue of their essentially compound character, be more 
correctly identified with the spicule-invested, compound, hiber- 
nating encystments or statoblasts (Carter), into which many 
sponge forms, including Spongillci , become resolved on the ter- 
mination of the season’s growth, and out of which are again 
liberated the flagelliferous elements that build up anew com- 
pound sponge-stocks. 
In conclusion. With those mycologists to whom every spore- 
capsule is necessarily a Fungus, and whose vision is sealed to 
every organism beyond their special line of research, the group 
of the Myxomycetes or Mycetozoa, will doubtless to the end of 
* It has been maintained by some advocates of the vegetable nature of 
the Myxomycetes, that these spicule-like structures differ in no way from 
the crystalline secretions of many plant-tissues known as 1 rhapliides.’ The 
unsoundness of such an interpretation is however made obvious in connexion 
with the fact that plant rhaphides are essentially m£n*-cellular secretions, 
while the spicular elements of both the Sponges and Mycetozoa are as strictly 
orfra-cellular developments. 
NEW SERIES, VOL. V. NO. XVIII. I 
