SCIENCE-GOSS/I'. 



1 1 



OVIPOSITION OF SOME HELICES. 



HpIIE animals and plants of the groups of 

 islands scattered over the Pacific Ocean 

 are often remarkable for the possession of 

 characters which are highly singular. Especi- 

 ally is this the case in the Sandwich and 

 Solomon groups, several of whose indigenous 

 animals and plants are, however, on the verge 

 of extinction through the encroachments of 

 cultivation. In the present note I wish to draw 

 attention to the remarkable habit possessed by 

 some Helices, belonging to the sections Libera and 

 Endodonta, of ovipositing in the umbilicus. Some 

 of the shells of the former section were exhibited 

 by me before the Malacological Society on July 

 14th, 1893 (" Proceedings," i., p. 4). 



The section Libera, containing about a dozen 

 species, all peculiar to the Society and Cook 

 Islands (Tryon's " Manual of Conchology " (2), 

 iii., p. 69) was established in 1881 by Andrew 

 Garrett, in the " Journal of the Academy of Natural 

 Sciences of Philadelphia " for that year, p. 390, 

 where he observes that the animals " are re- 

 markable for their singular habit of ovopositing 

 into their cavernous umbilici. The eggs, usually 

 from four to six, or the same number of very young 

 shells, may frequently be seen closely packed in 

 the cavity. The latter are shaped almost exactly 

 like a half-grown Planorbis trivolvis. The first 

 whorl is smooth, the second one with radiating 

 costulate striae ; and the internal laminae, both on 

 the penultimate and second whorl, can be distinctly 

 seen through the transparent shells. The peculiar 

 constriction of the umbilicus does not occur until 

 the last two whorls are completed, previous to 

 which it is very open or cup-shaped. Certain 

 species more completely secure the safety of the 

 eggs by the formation of a very thin shelly plate, 

 which projects from the columellar and parietal 

 region, and nearly closes the umbilical opening. 

 It is subsequently either broken away or absorbed 

 by the animal to facilitate the escape of the young 

 shells." 



The first mention of a habit of this kind, as far 

 as I have been able to discover, was made by 

 Morch, in the "Journal de Conchyliologie," 1865, 

 p. 395, and has reference to the allied section 

 Endodonta, which is, however, of much wider 

 distribution, being found not only in the Pacific 

 Islands but also in New Zealand, Tasmania, the 

 Malay Archipelago, the Philippines, and St. Helena, 

 and possesses a far greater number of species. His 

 note is to the following effect : — 



" Endodonta lamellosa, Fer, oviposits in the um- 

 bilicus, as also does another species from the 

 Sandwich Islands, communicated by Mr. Harper 

 Pease. In this latter the umbilicus was covered 

 by a sort of epiphragm." The shells of this 



section, not having the peculiar constriction of 

 the last two whorls as in Libera, their umbilici 

 are much wider and funnel-shaped, and it follows 

 that unless covered by an epiphragm the eggs 

 would be liable to become dispersed. This 

 epiphragm was observed in Endodonta by Garrett 

 also. In describing E. cretacea, he remarks that 

 " many of the adult shells have the umbilicus 

 covered with a thin brownish membrane, which in 

 all I have examined was perforated. Probably, as 

 in Libera, the animal oviposits in the umbilicus, 

 and covers it up with a membrane, and the per- 

 forations were made when the young animals 

 escaped. This peculiar feature has, so far, only 

 been observed in Borabora shells." (" Journ. Act 

 N.S., Phil.," 1884, p. 41.) 



Helix hevnemanni, enlarged and natural size. 



My attention was first drawn to this subject 

 when examining some Pacific shells received from 

 " Linnaea," of Berlin, and Hermann Rolle, of the 

 same place ; I noticed what I took to be debris in 

 the umbilici, but did not pay further attention 

 thereto until, when by accident I alighted upon the 

 above quoted note of Garrett, it occurred to me 

 that what I had regarded as debris might be eggs or 

 young shells. I therefore carefully examined all 

 the shells I had of the Libera and Endodonta groups. 

 Those of the former gave the following results : 

 Helix subcavernula, Tryon, Rarotonga (three 

 specimens), one with two young shells. H. cavernula, 

 Garr, Rarotonga (three specimens), one with one 

 young shell. H. hevnemanni, Pfr., Huahine (three 

 specimens), one with a lamellar plate (fig. a) 

 H. retunsa, Pfr., Tahiti (three specimens), one 

 with two young shells and one with one young 

 shell. H. tumuloides, Garr, Rarotonga (three 

 specimens), one with two young shells. II. 

 sculptilis, Pse., Rarotonga (three specimens), no 

 young shells. Those of the section Endodonta 

 yielded negative results only. 



The accompanying illustrations have been drawn 

 from specimens in my possession. a shows the 

 umbilicus covered with the lamellar plate referred 

 to above ; b, a specimen with the umbilicus open ; 

 while c represents an immature specimen in which 

 the last whorl has not yet been formed, and the 

 umbilicus is therefore very wide and open ; part of 

 the basal wall having been broken away shows the 

 internal lamellie on the parietal wall. 



G. K. Gudk. 

 5, Giesbach RluuI, Upper Holloway, .V. ,• 

 Ftb., 1S94. 



