216 PROF. HUXLEY ON THE AGAMIC REPRODUCTION 
force, or magnetic force, or od-force, to account for the existence of a mass of phenomena 
which will not arrange themselves under any of his established categories —forgetting that 
a * force,” the conditions of whose operation (that is, whose laws) are undetermined, is but 
a scientific idol, at once empty and mischievous,—empty, because it is but a phrase with- 
out real meaning; mischievous, because it acts as an intellectual opiate, confusedly satis- 
fying many minds and obstructing the progress of inquiry into the real laws of the 
phenomena. If we show that a fact is a case of a law, we explain that fact; but expla- 
nation by reference to an undefined * force,” of questionable existence, is simply ‘ignorance 
writ large.” 
Now, how does the hypothesis fulfil the indispensable conditions of a genuine explana- 
tion? In the first place, what proof is there of the existence of such a force as *sper- 
matic force.” All that we know is, that an ordinary ovum will not undergo those changes 
which constitute development without the contact of the spermatozoon. Hence it is 
concluded that some force contained in the spermatozoon is the efficient cause of all these 
changes. But what would be thought of the artillerist who should imagine he had ex- 
plained the propulsion of a bullet by saying it was ‘trigger force’? Or to take an 
illustration from phenomena of a like order to those under discussion: a seed will not 
grow unless it is exposed to a certain amount of warmth and moisture; but have I 
explained the growth by saying that it is the effect of ‘heat and moisture force’ which 
becomes diffused through the seed ? 
The very existence of this “spermatic force,” then, is a gratuitous assumption; and if 
we seek for its laws of action, we find but two stated: first, that it becomes weakened by 
the successive divisions of the germ-cell; second, that “the force is exhausted in pro- 
portion to the complexity and living powers of the organism developed from the primary 
germ-cell and germ-mass.”’ i Se 
I have shown to what singular consequences the first assumption leads us; it remains 
only to consider the second. If it be true, the occurrence of agamogenesis in the animal 
kingdom must bear an approximatively inverse ratio to the complexity of the organization 
of the different groups. Let us examine one or two subkingdoms in this point of view. 
Among the Annulosa, the Rotifera and Turbellaria possibly possess it to a small extent; 
the Nematoidea do not possess it at all. Many Trematoda possess it; others, such as 
Aspidogaster, have nothing of the kind. The Acanthocephala are not known to possess it; 
the Echinodermata are regarded by Prof. Owen as possessing it, but their different families 
show every gradation from simple metamorphosis to something like agamogenesis. A few 
Annelida possess the power in a marked degree; in many, nothing of the kind is known: 
en E: the Earth-worm and the Leech have it not. Of the Orustacea, Som 
x >ranehiopoda, exhibit it in the highest perfection ; but no trace of it an 
pr in. Copepoda, Cirripedia, Pæcilopoda, Edriophthalmia, or Podophthalmis: 
pos fe n N: and Arachnida the process is not known :- but we find it in the ROS 
ER = Soins this not, so far as we know at present, in Aptera or Ort E 
co FE So CURIE Hymenoptera and Lepidoptera ; and there is every reason 
Se y Nen in isolated, though perhaps in many, genera of these orders. 
| again: agamogenesis occurs in the Polyzoa and Ascidioida, not in the Bre 
