LIFE-HISTORIES AND THEIR LESSONS. 263 

Heterogenesis. Whereas, “ if it had been allowed to live it would 
have continued the process of self-division, until finally 
anew sporangium would have formed the commencement of a 
new series.” Again, Dr. Bastian affirms the small forms figured 
at //(Fig. 17), aré algoid vesicles budded off from Vaucheria, 
and that they “ gradually become converted into different kinds of 
diatoms.” And further, “these bodies increase in size, and it 
soon became obvious that they were young Naviculz (//); the 
exact pattern assumed in the early stages is subject to much varia- 
tion, and several different Diatoms seemed to be produced corres- 
ponding to these initial forms, mm.” (Fig. 17.) “This,” says 
Professor Smith, “would be wonderful if true; but not only is 
there no evidence that actual diatoms did come from the vesicles 
of Vaucheria, but any one familiar with the observation of living 
diatoms can tell where they did come from . . . They were 
in the gathering . . . and made their appearance out of the 
débris . . . as we know they will do under the influence of 
light . . . But, besides, diatoms do not grow by increase of 
size ; there are no such things as broods of young frustules . . . 
The late Dr. Greville . . . fully agreed with me in this.” 
Further, Fig. B, Plate V., is a copy of another illustration given 
in the Beginnings of Life. It is declared to represent the “resolu- 
tion of Euglena into diatoms.” It is said concerning it that 
“the whole of the contents of an Euglena seemed to have been 
resolved into distinctly striated Navicule . . . Although the 
earlier stages of the transformation were not seen (!), I have no 
doubt that the diatoms originated in this way.” Upon this Prof. 
Smith observes: “He (Dr. Bastian) is more easily satisfied that 
an Euglena can transform into a diatom, which possesses a won- 
derful silicious and beautifully sculptured epiderm, than he is that 
bacteria come from air-germs,” and then he clearly shows that the 
group of Navicule, seen in Fig. B, are simply a group that were 
devoured, and their protoplasm digested by an amceba. They con- 
stantly are ejected in this way from the body of the ameeba, after 
the nutrition has been abstracted, and look like an encysted mass 
with an envelope complete ; and even when treated with acids, al- 
though the envelope disappears, the frustules still adhere. And 
Professor Smith has “slides as well as materials, showing this in 
abundance.” All this, it may be presumed, is capable of suggest- 
ing two things: 1. The danger of attempting to discover new 
modes of “genesis” until we have made ourselves acquainted with 
the old ones; and 2. That “ Heterogenesis” is not even a scientific 
hypothesis, for the “facts” on which it is founded have not re- 
ceived scientific investigation.* But the caution suggested by all 
* “ Heterogenesis,” Popular Science Review, vol. xv., 346. 

