THE HISTOGENESIS AND CYCLIC PHENOMENA OF THE SINUS GLAND AND X-ORGAN IN CRUSTACEA

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Abstract
The histogenesis of the sinus gland and X-organ is descr. for the egg, 1st zoeal and adult stages in Pinnotheres maculatus, and for the egg, 1st 4 stages after hatching and adult stages of Homarus americanus. In Pinnotheres the X-organ is found adjacent to the medulla terminalis in the late egg stage; it maintains the same position in relation to the optic ganglia in all stages. During development the only change noted in the X-organ is an increase in the number of cells of which it is composed. It is not separated from the ganglia cells by a connective tissue sheath, nor is there any nerve fiber tract extending from it to the medulla terminalis. The sinus gland is present in the 1st adult stage as a well differentiated organ; in subsequent stages it moves more distally. In Homarus the X-organ is found in the late egg stage, and is comparable in many ways to that of Pinnotheres but is connected to the medulla terminalis by a nerve fiber tract and is separated from the surrounding ganglia cells by a connective tissue sheath. It increases in size and complexity as the animal matures. The sinus gland is found in the 3d stage after hatching as a simple structure. There is little change in it in the 4th stage; it is complex and large in the adult. Cytological examination of the sinus gland of Homarus and Pinnotheres as well as that of Cambarus virilis shows some evidence of cyclic phenomena associated with moulting in these spp. No such evidence is found in the X-organ which remains much the same at all times in regards to its staining reactions.