16 
INTRODUCTION. 
may exhibit a Hemitrichia-\\k.e capillitium ; and a specimen of 
Hemitrichia Serjmla from New Zealand, which has the appearance 
of having been affected by weather at the time of development, 
has a part of the capillitium consisting of short fusiform elaters. 
In some extensive gatherings of TricJiia affinis which have 
matured in hot, dry weather, the elaters are so reduced in size as 
scarcely to exceed the diameter of a spore in length, though the 
sporangia are perfectly normal in form, and the spores are marked 
with the typical sculpture. In Stemonitis, Lam2?roderma, Proto- 
trichia, and other genera, great variations are caused by changes 
of temperature ; but in none of these cases which have come under 
my observation is there any indication of a transition from one 
species to another. An interesting account is given by Dr. Hex 
of a remarkable and abnormal development of Stemonitis s2Jlendens, 
referred to under the description of that species in this work, 
where, through successive generations, a gradual return took 
place to the normal type. In this instance other causes than 
change of temperature must have taken part. 
Although the search for specimens of the Mycetozoa has 
been comparatively Hmited, owing, no doubt, to the small size 
of the objects, yet in consequence of the persistent nature of 
the sporangia, we possess, in the different herbaria, specimens 
representing the gatherings from many countries during more 
than half a centiiry, and some of them dating back to nearly 
a hundred years. Where they have escaped rough treatment, 
they completely retain their specific characters. In reviewing 
these specimens one is struck with the completeness of the 
group and the general stability of the species ; and when we 
consider their cosmopolitan distribution, owing, we may conclude, 
to the long-continued ^^.tality and minuteness of the spores, it 
may be doubted whether any hitherto unsearched region will add 
very largely to the number of species with which we are already 
acquainted. It is their life history which is at present imperfectly 
known, and it is in this direction that the important work of the 
future must lie. 
The affinities of the Mycetozoa have been dealt with by de Bary 
and Zopf in the works before referred to. 
It had been suggested that they were alHed to the fungi 
through the Chytrideo}, which do not always form a myce- 
lium, and in which the entii'e vegetative body is finally trans- 
formed into a many-spored sporangium, the vegetative body 
and spores having the power of amoeboid movement for a longer 
or shorter time. De Bary, however, mentions among other 
points of difference that the CliytricUoi do not form a Plas- 
modium by the coalescence of swarm-cells, " and there is there- 
fore no ground for assuming their direct relationship with the 
Mycetozoa." * 
The position of the Acrasiece in which the swai-m-cells exliibit 
* Do Bary, I.e. , p. 445. 
