1883.] Compound Organisms and their Lessons. 23 
impossible to answer. Yet what would thus puzzle and 
confound us in a cat is the common order of nature in the 
Nais . 
In the higher departments of the animal world, in the 
Mollusca, Arthropoda, and Vertebrata, we no longer find 
such distinct evidences of compound existence. Reproduc- 
tion by budding here no longer occurs, and the individual 
animal no longer consists of an aggregate of zooids which 
may lay claim, more or less plausibly, to the rank of inde- 
pendent organisms. 
Still the transition from compound or “ colonial ” to single 
unitary existence is not made abruptly. Certain remi- 
niscences, if we may so speak, of the earlier multiple life 
may be traced even in the highest animals. 
Suppose we take one of the simpler Annulosa, — say a 
centipede. We find it composed of a number of segments, 
or “ somites,” between which — save the head — and the last 
abdominal joint there is little difference. Each bears a pair 
of legs with their necessary muscular apparatus ; each has its 
pair of tracheae, forming a complete respiratory organ ; each 
contains a nerve-centre, or ganglion, differing relatively little 
in size and complexity from the brain. So far, then, each 
“ somite,” or joint as it is popularly called, possesses many 
of the characters of an independent being. But none of 
them, if severed from the rest, is capable of maintaining an 
independent existence or of surviving for more than a few 
hours. Reproduction is exclusively effected by means of 
eggs, secreted by especial organs, and in most cases it re- 
quires the concurrence of two individuals of opposite sexes. 
Budding has ceased, in as far as the production of an entire 
animal is concerned. At the same time we find a remnant 
of this mode of reproduction in the power of certain animals 
to develop new limbs or organs in place of such as have 
been mutilated or cut off. Thus the newt, if deprived of a 
leg or tail, can in time replace the missing organ. In snails 
the eyes, the tentacles, and the lips, if amputated, are com- 
pletely restored. But the higher we ascend the more does 
this power of partial reproduction fade away, and in man it 
plays a very insignificant part indeed. 
For all this the generation of certain of the Arthropoda 
presents us with a phenomenon which closely approximates 
to reproduction by budding as witnessed in the lowest ani- 
mals and in plants. We refer of course to parthenogenesis. 
It has been observed that several kinds of female insects lay 
fertile eggs without having had connection with a male of 
their species. This is pre-eminently the case with the 
