174 BULLETIN OF THE 



several between P. Garrettii Pse. and P. Thalia Garr. Mas. ; two between 

 P. faba Mart, and some unknown species ; besides a few others which I 

 cannot locate. 



Like many other Terrestrial Mollusks, Partulse are known as Vivipa- 

 rous Hermaphrodites, and on this account they may differ from bisexual 

 animals, in producing hybrids more or less fertile ; and we may hazard 

 the conjecture that some varieties of Partula originally may have re- 

 sulted from fertile hybrids, being the first step in the formation of a 

 race, afterwards intensified and rendered permanent by confinement to 

 the food and climatic influences of one station, and to having been 

 bred in and in, in such positions, for a long period. With respect to the 

 mutation of species of Mollusca caused by food and station alone, we 

 have a striking instance in the Achatinellas of the Sandwich Islands, a 

 genus in many respects analogous to Partula. It often happens that 

 " the gravid females are washed by heavy rains from a favored position 

 to drier levels, where after a few generations the progeny become depau- 

 perated, and so stunted in size as to be mistaken for distinct species." 

 The distribution of the different species of Partula throughout the Pa- 

 cific islands in some instances is not correctly ascertained ; and before 

 we can pronounce with certainty on the stations occupied by some 

 species, we must await a more thorough exploration of these islands, 

 the conchology of which has not been accurately observed. 



Andrew Garrett, Esq., of Huaheiue, who has resided and collected for 

 many years in the Polynesian Islands, contends " that, as the different 

 varieties of Partula are found in. limited areas, all those exhibiting slight 

 but constant differences should in most cases be acknowledged as dis- 

 tinct species." To this end he has kindly prepared the accompanying 

 maps to illustrate their distribution. The names underlined on the 

 maps indicate their metropolis or specific centre. A double line marks 

 the locality of a ground species. Partulce, like Trochomoi-jJia, Namna, 

 Helicina, S'nccinea, and some other Terrestrial Mollusks in tropical coun- 

 tries, are divided into Arboreal and Terrestrial species. The former 

 being Pound during the dry season gummed to the leaves and bark of 

 trees, while the latter are found at all times under decayed wood and 

 leaves. " The character of the animals affords but little aid in the de- 

 termination of species. In those of P. arguta Pse., P. turgids Pse., 

 P. annectens Pse., and P. gracilis Pse, the eiudation of mucus ia much 

 more viscid and tenacious than in other Bpecies. The ocular tentacles in 

 these are longer ami more slender, and the oolora of the soft part- as 

 seen through the pellucid shells are more variegated, than in the solid 



