LIFE-HISTORIES AND THEIR LESSONS. 175 

amongst the minute and unknown that the idea of heterogenesis 
is capable of being for a moment entertained ; and here it vanishes 
as our knowledge of the form involved becomes more clear, 
To know the life-history of any organism we must study that ; 
we must separate it from the crowd of other forms amidst which it 
flourishes, especially if amongst these there are organisms whose 
developmental history is not clearly known. Then observation 
should be continuous, not broken.’ Sequence in morphological 
development can only be certainly made out by unbroken obser- 
vation. Therefore, to do as some of our local observers have done, 
put Chara, Nitella, Vaucheria, or Desmids into a “live-box” with 
water, and keep them in a moist cell, and take them out for an 
hour’s observation to-day, and a couple or three hours’ observation 
to-morrow, and, because different phenomena present themselves, 
suppose them to be developmental sequences, is full of potential 
and actual error. The alge alone have hundreds of epiphytic 
algze parasitic upon and within them, whose life-histories are at 
present entirely unknown to us, and therefore, as the plants them- 
selves slowly decompose, we must of necessity become lost amidst 
the mazes of the mingled life and decomposition into which we 
are looking. 
Mr. Archer, of Dublin, a distinguished algologist, referring in- 
cidentally to these, says that they “are numerous and of common 
occurrence ; but the scientific world may not even yet possibly be 
aware of the newest ‘facts’ put forward by Dr. Bastian, as to their 
nature and origin (Beginnings of Life), who explains all in the most 
off-hand manner by gravely assuming that the varied and often very 
heterogeneous epiphytic fringes of algal form which are met with 
attached to higher plants, are developed as merely heterogenetic 
outgrowths from the latter!” 
But in attempting hastily to make inferences in favour of 
heterogenesis, still more glaring proofs of ignorance may show 
themselves. 
Amongst the lowliest of the fungi are the group Saprolegnia. 
The parasites composing it were until recently known as being 
chiefly confined to the bodies of insects, as flies, spiders, &c., in 
water. ‘They are now, however, known to infest the fish that 
inhabit our rivers, and are the actual cause of the “ salmon dis- 
ease’ recently so prevalent in England. As a group it is closely 
allied to the Leronospora, of which the fungus producing the 
European potato disease is a conspicuous example. For a long 
time both these groups baffled endeavour to decipher them, but 
at length Worthington Smith and Berkeley have succeeded in 
working through the life-cycle of the Lerenospora infestans, or 
potato fungus ; and De Bary has made out the history of a Sapro- 
legnia, or, as he prefers to call it, Achlya. But lowly as these 
