182 GKNUS IBLA. 



anomaly : the course of the oesophagus is approximately 

 represented in PL IV, fig. 8 a by faint dotted lines. 

 The stomach has no caeca; the biliary folds are longi- 

 tudinal ; there is a marked constriction at the line corre- 

 sponding with the junction of the thorax and prosoma. 

 There are no filamentary appendages. 



The generative system gives the chief interest to this 

 genus. We here first meet with Males and Females 

 distinct ; and, within the limits of this same restricted 

 genus, the far more wonderful fact of hermaphrodites, 

 whose masculine efficiency is aided by one or two Com- 

 plemental Males. The complemental and simple males 

 closely resemble each other, as do the female and herma- 

 phrodite forms ; but under the two following species I enter 

 into such full and minute details on these remarkable 

 facts, that I will not here dilate on them. I may add that, 

 at the end of the genus Scalpellum, I give a summary of 

 the facts, and discuss the whole question. The penis 

 (PL IV, fig. 9 a) in the hermaphrodite, I. quadrivalvis, 

 is singular, from the length of its unarticulated support, 

 and from the distinctness of the segments in the articu- 

 lated portion. 



As ovigerous fraena occur in the usual place in i". quad- 

 rivalvis, though much smaller than in any other species, I 

 have no doubt that they occur in I. Cumingii, although 

 I failed in observing them. The glands on the margin, 

 in L quadrivalvis, are singular, from not being borne on 

 a long, hair-like footstalk. 



Affinities. — Ibla, though externally very different in 

 appearance from Scalpellum, is more nearly related to 

 that genus than to any other; in both genera some 

 species have the sexes separate, the imperfect males being 

 parasitic on the female, and other species are bisexual or 

 hermaphrodite, but aided by parasitic complemental 

 males. In Scalpellum, again, the oesophagus pursues a 

 sinuous course, resembling that in Ibla, though it does 

 not pass exteriorly to the adductor scutorum muscle. 

 The disc of the prehensile antennae of the larva, in 



