Proseguendo le ricer he nel 1919 la Thompson studia lo sviluppo c stale di tre- 
dici specie di termiti «ppartenenti a nove generi diversi (7ermopsis, Calotermes, Crypto- 
termes, Neotermes, Arrhinotermes, Reticulitermes, Anoplotermes, Amitermes, Eulermes) e 
a tutti estende le sue conclusioni (214). 
E non si limita a dedurne che l’origine ontogenetica delle caste di neutri è dovuta 
esclusivamente ad intrinseche cause indipendentemente da estrinseci stimoli; ma, con 
processo di generalizzazione inverso a quello pel quale dallo studio dei reali neotenici 
il Grassi aveva indotto che anche la differenziazione dei neutri avviene nel corso dello 
sviluppo per cangiamento della nutrizione, conclude che tutte le caste sono predeter- 
minate nell'uovo, anche quelle che sembrano manifestarsi più tardi, nel corso dello svi- 
luppo. 
« My final conclusion is that all termite castes are predetermined in the eggs ; that 
some castes are distinguishable, cither by external'or internal characters, at the time of 
hatching, while others may appear considerably later in the course of development. In 
Leucotermes the more generalized castes are the first to be manilested, the more specia- 
lized are later in their appearance » (pag. 130, 223). 
« The conversion of the ‘undifferentiated ? nymphs, by feeding, into large and small 
headed forms, and these again into the future adult castes ; the production of ‘ substitute 
reproductive forms from an ever present ‘reserve’ of “indifferent larvae, or by the alte- 
ration of forms whose development has already begun ; the sudden and opportune appea- 
rance of ‘substitute forms’ in ‘orphaned nests  ; all these assumptions, which, indeed, ap- 
peal to our sense of the dramatie and marvellous, must now be regarded as possessing 
chiefly an historic interest » (pag. 126, 273). 
a, the bulk of the brain ; 5, the relative size of brain and head ; c, the structure of the compound eyes ; 
and d, the size oî the sex organs. 
3. « The reproductive type ot newly hatched nymph has a large brain, in which the mushroom 
bodies, optic lobes and antennary lobes are all large. The space within the hypodermis of the head is 
nearly filled by the brain. The compound eyes are slightly larger than in the worker-soldier type. 
4. « The worker-soldier type ot newly hatched nymph has a small brain, with small mushroom 
bodies, optic lobes and antennary lobes. The space within the hypodermis of the head is not nearly 
filled by the brain. The compound eyes are smaller and simpler, and the sex organs are smaller than in 
the reproductive type. 
5. « The antennae of the newly hatched nymphs of both L. flavipes and L. virginicus are com- 
posed of nine segments, the third segment grooved and bare. 
6. «Innymphsof I. flavipes with ten antennary segments, the third segment grooved, and a body 
lenght of 1,3 to 1, 4mm., the individuals of the reproductive type are further differentiated intotwo 
groups: a, with large brain and large sex organs ; d, with slightly smaller brain and smaller sex organs. 
These are the respective prototypes of the nymphs of the first form and the nymphs of the second form, 
and hence of the two adult castes oÈ the first form, with long wings, and of the second form, with 
short wing pads. 
7. «The prototypes of the worker and soldier castes, although externally alike, are distingui- 
shable by internal structures at the end of the second stage of development, in nymphs with a body 
lenght ot 3,75 mm, and are probably distinguishable at an even earlier age » (pp. 131-132 Summary 
of results, 213). 
