§4.213 ECTODERMAL ENDOCRINE GLANDS OF ARTHROPODA 135 



though the former, which concern protein metaboHsm (§ 5.2) and 

 calcium distribution (§ 5.4), are intimately related to its main 

 action as a moult-promoting hormone (Part II, § 3). Without its 

 secretion, neither moulting nor regeneration can occur (Echalier 

 1956). It is inhibited, or its action is overridden, by the moult- 

 inhibiting hormone from the sinus gland ; but it can secrete when 

 its nerve supply has been severed. This last observation suggests 

 that it may be subject to some hormonal stimulation, such as might 

 be exerted by Hanstrom's sensory pore organ, which secretes a 

 MOULT-ACCELERATING HORMONE in Lysmata and Leander; but 

 there is only presumptive evidence for naming the latter as a true 

 endocrinokinetic hormone, capable of stimulating the secretion 

 of the Y-organ (Knowles and Carlisle, 1956). 



4.212 Ventral glands stimulated by a secretion from the siiboeso- 

 phageal ganglion 



Insecta. The maxillary ectodermal glands which secrete the 

 moult-promoting hormone, ecd3'Sone, in the more primitive 

 orders, Ephemeroptera and Odonata, retain their original ventral 

 position in the head (Fig. 2-8). Unlike their homologues in other 

 orders of insects, they are stimulated to secrete by neurosecretory 

 cells in the suboesophageal ganglion, instead of in the brain. The 

 axons of these cells connect directly with the ventral glands 

 (Gabe, 1953) and probably release a neurohormone (§ 1.2), since 

 they are only effective if the axons remain intact. A rich source for 

 extracts of the neurohormone has been found in the ganglion 

 (Arvy and Gabe, 1954), but a vascular endocrinokinetic hormone 

 has not been shown. 



4.213 Peritracheal and prothoracic glands stimulated by a secretion 

 from the inter cerebrurn 



Insecta. Despite the differences in their final positions (Fig. 

 2-8), these glands appear to be homologous with each other and 

 to be derived from ectodermal intuckings in the 2nd maxillary 

 (or labial) segment, like the ventral glands and some of the 

 crustacean Y-organs. The peritracheal glands form part of 

 Weismann's ring in Diptera, such as Calliphora. Prothoracic 

 glands occur in most other genera, of which Rhodniiis, Hyalophora 



