198 The Molluscan Family Planorhidae 



row tube freely movable within the vergic sac (VS). This organ was en- 

 tirely misunderstood by Rao and was not fully comprehended by the writer 

 (Baker, 1933). Larambergue (1939, p. 288) correctly figures the relation- 

 ship between the vergic sac (poche de penis) and the verge (tube penial), 

 the latter being much longer than figured by Baker and extending the 

 whole length of the vergic sac. 



The writer figured and described a bulbous swelling within the vergic 

 sac (plate 21, fig. 1, B) which was thought to be the termination of the 

 verge, the tube behind this swelling being considered as a part of the vas 

 deferens. Larambcrgue's figure 2 (reproduced as fig. 2 on plate 73 of this 

 work) shows that this is not the case and that the whole tube must be 

 considered the verge. However, this bulbous portion of the verge was pres- 

 ent in all specimens examined and a swelling of this region is shown in the 

 figure of Larambergue where the long line for the symbol pe is directed. 

 It seems probable that this bulbous portion (use unknown) is found in all 

 examples of Indoplanorhis but in the specimens examined by Larambergue 

 there was less contraction than in the specimens examined by Baker. In 

 other words, the differences may be attributable to methods of preservation. 



Two specimens examined by Baker had the preputium completely 

 everted from the male opening, the sac lying on the body of the animal, as 

 shown in fig. 2 of plate 21. One of these specimens is shown in optical sec- 

 tion in fig. 7 of plate 22. In this specimen, the preputium was greatly 

 flattened so that the pilasters (AIP) became two flattened muscular pads, 

 filling the greater part of the preputial cavity. The verge (V) and vergic 

 sac (VS) extend through the preputium nearly to the opening of the 

 preputium (PR). The bulbous portion of the verge is conspicuous and has 

 moved downward. The retractor muscle is attached to the vergic sac near 

 its distal end and the large nerve lies beside it (RM, N) . It is clearly 

 evident that this muscle pulls back the male intromittent organ after 

 copulation. A cross section of the preputium near its widest part is shown 

 in fig. 6. The branching of the retractor muscle and the connections of the 

 nerve are shown in fig. 5, greatly enlarged. The so-called supporting mus- 

 cles of the preputium apparently become retractor muscles when the 

 verge and the preputium are everted (fig. 5, plate 21). 



Larambergue (1939, p. 293) describes and figures the penial complex 

 in the everted position (see plate 74, fig. 6). The vergic sac is shown ex- 

 tended from the everted end of the preputium. The everted copulatory 

 organ is enlarged at the distal end, being almost twice the diameter of 

 the proximal end near the preputium. A trifle more than half of the length 

 of the vergic sac is everted, the shorter portion remaining within the 

 preputium and body during eversion. These drawings of Larambergue 

 were made from freshly anesthetized specimens taken in coitus. 



Observations on the specimens dissected by the author do not entirely 

 agree with those of Larambergue. In several specimens, the verge extended 

 from the vergic sac and protruded into the perputium for some distance 

 (plate 21, fig. 1). Rao (1923, p. 215) figures the verge (penis) as pro- 

 truding from the vergic sac into the preputial cavity. He also figures the 

 retractor muscle as attached to the vergic sac and not to the preputium. 



It has been the writer's opinion that only the verge was protruded from 

 the end of the preputium when the latter was everted from the male open- 

 ing. The retractor muscle is shown by Larambergue as attached to the 

 upper end of the preputium, while in all specimens personally examined 



