ANDROGYNOUS MOLLUSCA. 365 



My own observation agrees with what Bradley tells us of 

 these amatorculists : " The manner of their meeting to 

 couple is well worth observing ; in dewy evenings, or after 

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

 manner, making several rounds, till they come near enough 

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

 sometimes make above twenty turns before they could 

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

 frequently find the dart sticking in the neck of the snails, 

 or merely adhering to the skin by the tenacity of its mucus, 

 for the penetration of the point is very slight; nor do I 

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

 with the conjectures that have been oifered. 



The spawn of the aquatic tribes, whether of the fresh 

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

 are 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- 



dart penetrated; though at the time the animals are close the point may 

 irritate ; but it is neither sufficiently strong nor sharp-pointed to penetrate 

 the tough skin with which these animals are furnished." MONTAGU, Test. 

 Brit. 410. See also Miiller Verm. Fluv. and Ter. ii. pref. xiii., and Dra- 

 parnaud's Hist, des Mollusq. p. 6, 7. Blumenbach has figured the dart of 

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

 accurately in the anatomical plate ii. of his Hist. Conchyliorum. 



* Phil. Account, p. 127. The manner of courtship is, however, often 

 less formal ; and few can have leisure or patience to watch their tardy ad- 

 vances. I need only refer to Swammerdam's account of them. 



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

 is good enough to be quoted : " The spawn, when first deposited, appears 

 to the naked eye like a transparent jelly ; but if examined by the micro- 

 scope one sees in it numbers of small and exceedingly pellucid oval bodies, 

 at little distances from one another, inveloped in a gelatinous substance ; 

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

 speck, wherein, if carefully examined by the greatest magnifier, a pulsation 

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

 day and to become a perfect snail, with its shell complete, several days 

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

 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 oblong bladder, much less at one end than the 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 pulsations being performed in a 

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

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

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

 creasing in bulk and becoming consequently more opaque, in some positions it 

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



