636 BRITISH ASSOCIATION FOR ADVANCEMENT OF SCIENCE. 
fact of the development of parasitic animals in the flesh, brain, and glands 
of higher animals. But the hypothesis never obtained currency in this 
country ; it was publicly opposed in my c Hunterian Lectures,’ by the fact 
of the prodigious preparation of fertile eggs in many of the supposed spon- 
taneously developed species ; and in then suggesting that the Trichina spira- 
lis of the human muscular tissue might be the embryo of a larger worm in 
course of migration, I urged that a particular investigation was needed for 
each particular species. 
Since the time when it was first discovered that plants and animals could 
propagate in two ways, and that the individual developed from the bud 
might produce a seed or egg, from which also an individual might spring 
capable of again budding, — since this alternating mode of generation was 
observed, as by Chamisso and Sars, in cases where the budding individual 
differed much in form from the egg-laying one — the subject has been syste- 
matized, generalized, with an attempt to explain its principle, and greatly 
advanced, especially, and in a highly interesting manner, in Yon Siebold’s 
late treatise, entitled ‘Wahre Parthenogenesis bei Schmeterlingen und 
Bienen,’ in which the virgin production of the male or drone-bee is demon- 
strated. Yon Siebold, having subjected to the closest microscopic scrutiny 
and experiment the conclusion to which the practical Bee-master Dzierson 
had arrived, relative to the cause of queen-bees with crippled wings pro- 
ducing a swarm exclusively of drones, has demonstrated that the male bee 
is produced from an egg which has been subjected to no influence save that 
of the maternal parent ; whilst such egg, if impregnated, would have pro- 
duced a female or worker bee. The now well-investigated phenomena of 
parthenogenesis in Hydrozoa have resulted in showing, as in the analogous 
case of Bntozoa, that animals differing so much in form as to have constituted 
two distinct orders or classes, are really but two terms of a cycle of metagenetic 
transformations — the acalephan Medusa being the sexual locomotive form of 
the agamic rooted budding polype, just as the cestoid taenia is of the cystic 
hydatid. In Hydrozoa (hydroid polypes or sertularians) the young are propa- 
gated, as in plants, by “ buds,” and also, as iu most plants, by “germs ” or 
“ seeds these latter are contained in “ germ-sacs ” projecting from the outer 
surface, which is another analogy to the flowering parts of plants. The first 
acquaintance with these marvels excited the hope that, we were about to pene- 
trate the mystery of the origin of different species of animals ; but as far as 
observation has yet extended, the cycle of changes is definitely closed. And, 
since one essential step in the series is the fertilized seed or egg, the Harveiau 
axiom, “ omne vivum ab ovo ,” if metagenetic phases be ascribed to one indi- 
vidual, may be still predicated of all organisms which bear the unmistake- 
able characters of plants or of animals. The closest observations of the 
subjects of these two kingdoms most favorable to clear insight into the 
nature of their beginning, accumulate evidence in proof of the essential first 
step being due to the protoplasmic matter of a germ-cell and sperm-cell ; the 
former pre-existing in the form of a nucleus or protoplast, the latter as a 
granulose fluid. In flowering plants it is conveyed by the pollen-tube, in 
animals and many flowerless plants, by locomotive spermatozoids. The 
changes of form which the representative of a species undergoes in succes- 
sive 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 sup- 
posed essential differences in the metamorphoses of insects, it had been 
suggested that stages answering to those represented by the apodal and 
