Ixxvi REPORT—1858. 
In regard to lower living things, analogy is but hazardous ground for con- 
clusions. The single-celled organisms, such as many of the so-called ani- 
malcules of infusions, which are at a stage of organization too low for a definite 
transfer to either the vegetable or animal kingdoms, offer a field of obser- 
vation and experiment which may yet issue in giving us a clearer insight 
into the development of the organic living cell. 
Whether an independent free-moving and assimilating organism, of a 
grade of structure similar to, and scarcely higher than the ‘ germ-cell,’ may 
not arise by a collocation of particles, through the operation of a force ana- 
logous to that which originally formed the germ-cell in the ovarian stroma, 
is a question which cannot be answered until every possible care and pains 
have been applied to its solution. 
The changes of form which the representative of a species undergoes in 
successive agamically propagating individuals are termed the ‘ metagenesis’ 
of such species. The changes of form which the representative of a species 
undergoes in a single individual is called the ‘metamorphosis.’ But this 
term has practically been restricted to the instances in which the individual, 
during certain phases of the change, is free and active, as in the grub of the 
chaffer, or the tadpole of the frog, for example. 
In reference to some supposed essential differences in the metamorphoses 
of insects, it had been suggested that stages answering to those represented 
by the apodal and acephalous maggot of the Diptera, by the hexapod larva 
of the Carabi, and by the hexapod antenniferous larvee of the Meloe were 
really passed through by the orthopterous insect, before it quitted the egg*. 
Mr. Andrew Murray ¢ has recently made known some facts in confirma- 
tion of this view. He had received a wooden idol from Africa, behind the 
ears of which a Blatta had fixed its egg-cases, after which the whole figure 
had been rudely painted by the natives, and these egg-cases were covered by 
the paint. No insect could have emerged without breaking through the case 
and the paint; but both were uninjured. In the egg-cases were discovered,— 
1st, a grub-like larva in the egg; 2nd, a cocoon in the egg containing the 
unwinged, imperfectly-developed insect; 3rd, the unwinged, imperfectly- 
developed insect in the egg, free from the cocoon, and ready to emerge. 
Such observations tending to remove supposed exceptions and anomalies, 
and to illustrate and establish the common law to which they can be reduced, 
are of the highest value in Natural History. 
Microscope.—The microscope is an indispensable instrument in embryolo- 
gical and histological researches, as also in reference to that vast swarm of 
animalcules which are too minute for ordinary vision. I can here do little 
more than allude to the systematic direction now given to the application of 
* Owen, “ On Metamorphosis and Metagenesis,” 1851, and “ Lectures on Invertebrata,” 
vo, 1855, p. 424. 
+ “On the Metamorphosis of Orthopterous and Hemipterous Insects,” Edinb. Phil. 
Journal, 1858. 
