72 HUXLEY, ON CLASSIFICATION. 
becoming slightly pointed at each end, constitutes a little body 
which has been called a “‘ Pseudo-navicella,” from its resemblance to 
the Diatomaceous Navicula or Navicella (Fig. 1, C, D). Next, the 
capsule bursts and the Pseudo-navicelle (Fig. 1, E, F) are scattered 
and passed out of the body of the animal which they inhabit. 
Though, of course, a great number of them are destroyed, some, at 
any rate, are devoured by other animals; and, when that is the case, 
the little particle of protein substance which is inclosed within the 
Pseudo-navicella is set free from its shell, and exhibits much more 
lively movements than before, thrusting out processes in various 
directions, and drawing them in again, and, in fact, closely resem- 
bling one of those animalcules which have been called Amebe (Fig. 
1, H). The young Amebiform Gregarina grows, increases in size, 
and at length assumes the structure which it had at first. That, in 
substance, is all that we know of this lowest division of animal life. 
But it will be observed, there is a hiatus in our knowledge. We 
cannot say that we know the whole nature and mode of existence of 
this, or any other animal, until we have traced it to its sexual state; 
but, at present, we know nothing whatever of this condition among 
the Gregarine ; so that in reasoning about them we must always 
exercise a certain reticence, not knowing how far we may have to 
modify our opinions by the discovery of the sexual state hereafter. 
The process of becoming encysted, preceded or accompanied very 
often by the mutual apposition of two Gregarine, was formerly 
imagined to correspond with what is termed among plants “ conjuga- 
tion,”’—a process which in some cases, at any rate, appears to be of 
a sexual nature. But the discovery that a single Gregarina may be- 
come encysted and break up into Pseudo-navicelle seems to negative 
this analogy. 
But now, leaving this, I pass on to the next class—that which is 
indicated in the table asthe Ruizopopa. Ihave puta query against 
it, as I shall have to return to it as another of those respecting which 
our knowledge is incomplete. And at this moment I merely direct 
attention to the salient and characteristic features of the whole 
group (Fig. 2). 
It seems difficult to imagine a stage of organization lower than that 
of Gregarinida, and yet many of the Rhizopoda are stillsimpler. Nor 
is there any group of the animal kingdom which more admirably 
illustrates a very well-founded doctrine, and one which was often 
advocated by Hunter himself, that life is the cause and not the con- 
sequence of organization; for, in these lowest forms of animal life, 
there is absolutely nothing worthy of the name of organization to be 
discovered by the microscopist, though assisted by the beautiful in- 
struments that are now constructed. In the substance of many of 
