Dr. David Sharp's Studies in Rhijnchophora. 213 



of the genital tube with the body wall, and a peculiar 

 structure the spiculum gastrale. All these have origin 

 from a membranous area at the tip of the abdomen, and 

 this small and irregularly shaped membrane must be 

 treated as common to all the structures. On severing this 

 membrane so as to free the genital tube from the other 

 parts, we expose the tegminal layer of the genital tube 

 (the Paramerenrohr of Ninslin). As this is the commence- 

 ment of the genital tube it is well to remark that the pos- 

 terior part of the tube is functionally its anterior part, as 

 shown in fig. 2. This complication as to the orientation 

 renders it desirable to use the terms basal and apical 

 instead of anterior and posterior; basal being nearer to 

 the centre of the body than apical is. 



The spiculum gastrale is at once seen ; it is the ' ' Stengel 

 of Lindeman, the "fork" according to Hopkins, the 

 "spiculum" of Verhoeff and Ninslin. It is present in 

 the great majority of Rhynchophora, but is absent in some 

 of the Calandridae, especially in those of very large size, 

 and it is also wanting in Platypidae. It is a curved 

 or sinuate rod, connected at the apical area, mentioned 

 above, with the tube at or near the base of the latter 

 when extended ; it is of variable size according to the 

 species, and extends basally, its sinuation adapting it to 

 some extent to keep close to the tube, its musculature 

 is great. At its apex it forms a sort of fork with widely 

 separated, short prongs; but there are various forms in 

 which this structure is peculiar (cf. Naupactus and to a 

 less extent Episomus). This part is closely connected 

 with the true last ventral plate, and this connection appears 

 to be not always a simple one. This structure is much in 

 need of investigation, especially as some anatomists con- 

 sider the spiculum to be a modified ventral plate (the 9th). 

 At the other (or basal) extremity the spiculum is generally 

 somewhat expanded and more abruptly curved, and some- 

 times greatly so. The spiculum diverges from the teg- 

 minal layer, of which I consider it to be a part, just as the 

 strut of the tegmen is a part of the tegmen. 



The Tegminal Layer. 



This part of the tube connects with the apex of the 



abdomen. It does not reverse or extend when the organ 



is functioning, but is held in place by its connections, 



including the spiculum and the true last ventral, so that 



