ANDROGYNOUS MOLLUSCA. *^05 



My own observation aj^rccs wilh what Bradley tells_ us of 

 these aniatoreulists : — "The manner oi" their meeting to 

 couple is well worth observinj^- ; in dewy eveninf,^s, or after 

 a shower of rain, they crawl upon the grass in a circniar 

 manner, uiaking several rounds, till they come near enough 

 to one another to hit their design : I have observed tluin 

 sometimes make al)ove twenty turns before they could 

 join."* After the union has been dissolved, you may 

 fre(|uently find the dart sticking in the neck of the snails, 

 or merely adhering to the skin by the tenacity of its nuu-us, 

 for the ])enetration of the ])oint is very slight; nor do J 

 know what the true use of the dart is, being little pleased 

 with the conjectures that have beeii offered. 



The spawn of the aquatic tribes, whether of the fresh 

 waters or of the sea, is a gelatinous mass, in whicli the ova 

 arc imbedded in a manner similar to that of the Littorina 

 vulgaris. f The jelly seems to have some peculiar qualities, 

 — to be a substance intermediate between albumen and gela- 



(liirt ponetratcd ; tlioiigli at tlu; time tlio nnimal.s nro close tlio point may 

 irritate ; but it is neitlier suflicicntly strong nor sliar])-]iointe(l to penetrate 

 tlic tougli skin witli whieli tiiesc animals are furnisiied." — Montagu, Test. 

 Urit, 410. See also Miiller Verm. l<"lnv. and Ter. ii. pn:!'. xiii., and Dra- 

 parnauil's Hist, des Mollnsq. p. (J, 7.— IMumenljacli has figured tiie dart of 

 the common snail in his Elem. Nat. Hist, trans. y\. 1. fig. 8 ; and Lister more 

 accurately in the anatomical ])hite ii. oI" iiis Hist. Conciiyliorum. 



* Phil. Account, p. 127. — 'I'iie manner of courtshij) is, however, oftiMi 

 less forniid ; and few can have leisure or patience to watch their tar<ly ad- 

 vances. I need only refer to Swannuerdam's account of tliem. 



t Baker has given a description of the spawn of Limneus putris, which 

 is goo<l enough to be quoted : — " The spawn, when first deposited, app(>ars 

 to the naked eye like a transparent Jelly ; but if <:xamincd ijy liie micro- 

 scope one sees in it numbers of snnill and exceedingly pelhicid oval bodies, 

 at litde distances from one anotiier, inveloped in a gelatinous .substance ; 

 having each of them towards one of its extremities a very mimite dark 

 speck, wherein, if carefully examine.l by the greatest magnifier,_a pulsation 

 may be discerned. This speck will be foimd to grow larger from day to 

 (lay and to become a ]»erfect snail, with its shell complete, several days 

 before it bursts through its integuments. When the eggs are about a weLd< 

 old the embryo snail may be discerned in its true shape, turning itself very 

 frequently within the fine fluid in which it lies ; and the heart is then a 

 most agreeable and amazing spectacle, shewing itself very distinctly and 

 resembling a little olilong Idadder, nmch less at one end than tiie other : the 

 pulsation proceeds under the eye with great exactness and regularity, and 

 the systole and the diastole of this vessel are nearly equal to those of the 

 human heart, somewhat more than sixty nulsations being performed in a 

 minute, as I have found by several trials, Iceeiting my finger at the same 

 time on my own pulse, which usually beats one or diree strokes more. The 

 heart is large in jiwiportion and may be always seen, until the animal in- 

 creasing in l)ulk and becoming eonseipiently more opaque, in .some [lositions it 

 hardly can be perceived ; but as the animal frecpienlly turns itself within 



