Development of CI Termite. 'i.'^X 



ance of appendages, in detail, as yet, but may state that the 

 central nervous system arises from neuroblast cells, as 

 described by Viallanes (7) and Wheeler (9) for certain of the 

 Orthoptera. 



I had hoped to make out the history of the reproductive 

 system ; but, as far as can be determined, no trace of these 

 organs is developed until sometime after hatching. In the 

 workers and soldiers (nasuti), both larvse and adult, of this 

 species the reproductive organs are entirely aborted. 



In reference to the general bearings of my study of this 

 form I shall have something to say in the paper of which 

 this is a preliminary abstract. It may be said here that I do 

 not regard the Libellulids as the best examples of the ancestral 

 type of development among insects, as has been so promi- 

 nently claimed of late (4) (Korschelt and Heider). On the 

 contrary, 1 think that the termite and those Orthoptera 

 having a superficial embryo beginning in a disk which must 

 elongate considerably to attain the definitive number of 

 segments have most nearly adhered to the typical method of 

 development for arthropods, and probably best represent the 

 development of the ancestral insects. My reasons for this 

 cannot be given in this note, but will appear in the full paper. 



There is not sufficient space here to discuss the question of 

 the origin of the amnion, but I will say that Wheeler's (9) 

 adaptation to insects of Ryder's theory of a mechanical origin 

 of the membranes of vertebrates seems a most inadequate 

 explanation. (Of course the word " mechanical," as used 

 here, is used in the narrow sense of the terra, referring the 

 subject to simply stated conditions of pressure and mechanical 

 strain.) This theory is opposed by what we know of the 

 development of the Crustacea, the Myriopods, and the 

 Apterygota. As far as can be shown, the same conditions of 

 pressure are brought to bear on the developing embryos of 

 these forms as on those of the amniote insects ; yet no 

 amnion is formed. In those higher forms of insects, which 

 are characterized by the non-appearance of membranes, their 

 failure to appear is even more marked. Here, in the very- 

 face of the conditions stated to be efficient to produce them, 

 no membranes are developed. 



The origin of the amnion is in all probability referable to 

 physico-chemical forces ; but at present I do not believe the 

 problem can be stated in more definite terms than as follows: — 

 There was a suitable basis among tlie anamniotic ancestors of 

 winged insects for the formation of membranes, but a further 

 condition was necessary before the amnion should arise. 

 This was a change in the environmental influences, making 



