B. T. LOWNE ON THE HYMENOPTERA. 189 



then the portion which represents the tail becomes split into two, 

 and at length three pairs of lateral appendages are formed as buds, 

 whilst a pair of hnigitudinal bristles spring from the tail. In the 

 meantime a hollow has been formed in the interior, which will be- 

 come the alimentary canal. 



The egg now hatches, the larva comes out, and swims about in 

 the interior of the host. On referring to Mr. Ganin's figures, 

 which have been reproduced in " Nature" since this paper was 

 read, you will, I think, at once see the resemblnnce which this 

 larva bears to an ordinary cyclops, and it certainly bears a very 

 curious resemblance to several forms of Crustacea. Three or four 

 of the eggs are generally laid in the body of one cecidomyian larva, 

 and when the host has been destroyed by them and no more re- 

 mains to be eaten, they fall to upon one another ; the weakest goes 

 to the wall, until at last there is only one left. There is still only 

 a very rudimentary alimentary canal ; the whole creature, in fact, 

 remains very rudimentary up to this stage of development. 



The cellular walls of the embryo-platygaster now begin to 

 undergo differentiation, and the changes which take place are very 

 like those which take place in the blastoderm of an ordinary 

 insect's egg. In fact, this cyclops-like larva may be looked upon 

 as a kind of living egg shell, in the interior of which a new 

 creature is being developed. This may at first appear so strange 

 as to be incredible, but similar instances of such development are 

 well known ; an excellent example of this phenemonon is seen in the 

 case of the common star-fish. In its early stage it is called a 

 Pluteus, and it is in the interior of this larva or embryo that the 

 star-fish undergoes development, by the growth and development of 

 new formed embryonic cells. To recur to onr Platygaster,the next 

 change consists in the shedding of the cyclops-like integument, 

 and the new embryo becomes remarkable for its entire want of 

 segmentation, so that it looks more like one of the lower forms of 

 worms. After this a further change takes place, a new skin is 

 again formed, which this time is entirely hymenopterous ; the 

 creature has now become a thoroughly hymenopterous larva, and 

 having passed through the usual transformations emerges at 

 length as a perfectly formed Platygaster. This is certainly an 

 extremely curious and remarkable life history, and one which I 

 believe will one day throw much light upon the question of the 

 evolution of insects. The curious resemblance in the course of 



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