REVIEWS. 51 
recently shown by Von Grimm, a fellow countryman of Ganin, to 
produce young in the spring, while the adult fly lays eggs in the 
autumn in the usual manner. This is in fact a true virgin repro- 
duction, and directly comparable to the alternation of generations 
observed in the jelly fishes, in Salpa, and certain intestinal worms. 
We can now, in the light of the researches of Ganin, Siebold, 
Leuckart, and others, trace more closely than ever the connection 
between simple growth and metamorphosis, and metamorphosis and 
parthenogenesis, and perceive that they are but the terms of a sin- 
gle series. By the acceleration of a single set of organs (the repro- 
ductive), no more wonderful than the acceleration and retardation 
of the other systems of organs, so clearly pointed out in the em- 
bryos of Platygaster and its allies, we see how parthenogenesis 
under certain conditions may result. The barren Platygaster- 
larva, the fertile Cecidomyia larva, the fertile Aphis larva, the 
_ fertile Chironomus pupa, the fertile hydroid polyp, and the fertile 
adult queen bee, are simply animals in different degrees of organi- 
zation, and with reproductive systems differing not in quality, but 
in the greater or less rapidity of their development as compared 
with the rest of the body. 
Another interesting point is, that while the larvee vary so re- 
markably in form, the adult ichneumon flies are remarkably simi- 
lar to one another. Do the differences in their larval history seem 
to point back to certain. still more divergent ancestral forms? 
These remarkable hyper-metamorphoses remind us of the meta- 
morphosis of the embryo of Echinoderms into the Pluteus- and 
Bipinnaria-forms of the star-fish, sea-urchins, and :Holothuriæ ; 
of the Actinotrocha-form larva of the Sipunculoid worms; of the 
Cerearia-form larva of Distoma; of the Pilidium-form larva of 
Nemertes; and the larval forms of the leeches ;* as well as the 
acarian Pentastomum, and certain other aberrant mites, such as 
Myobia, and in a less degree certain other more highly organized 
mites, such as Atax, and Hydrachna, and the ticks, which may 
almost be said to, pass through a byper-metamorphosis. 
‘While Fritz Miller and Dohrn have considered the insects as 
having descended from the Crustacea (some primitive zoéa-form), 
* Leuckart, in his great work, “ Die Menschlichen Parasiten,” p. 700, after the anal- 
ogy of Hirudo, which Tam a primitive streak late in larval life, ventures to con- 
sider the first indications o f the germ o of Nemertes in its larval, P. Pilidinm-form as a 
primitive streak. He al hat the develop t he | 1 ul fi f th 
Echinoderms is the same in ‘kind. 
