234 PATELLIDJE. 



for 1846 furtlier particulars of its reproductive organs. 

 The last-named physiologists noticed that at the end of 

 April these organs (which in each sex are placed at the 

 left-hand side of the body) were Avanting in nearly one- 

 half of the indiAdduals dissected by them^ and that of 

 the remainder the males were in the proportion of 3 to 

 8 or 10 of the females. Fischer has given us some 

 information as to the mode of its oviposition. This 

 takes place in the months of March and April, when all 

 the rocks at low water, as well as the shells of old 

 limpets, are covered with an immense quantity of the 

 fry. He is of opinion that immediately on the eggs 

 being excluded from the ovary, they are developed and 

 attach themselves. Gray suspected the sexes to be 

 distinct in the limpet ; although he could not discover 

 any external difference in the animals, except a slight 

 variation of colour. He says that in autumn he found 

 a white, milky, glairy fluid in some individuals, and ova 

 in others. My late friend Dr. Lukis noticed, in taking 

 up a limpet while in the act of crawling, that young 

 ones were attached to the under side of the foot ; and he 

 inferred that it carried its offspring about with it for 

 protection. But it is more probable that the fry became 

 accidentally entangled in the gelatinous fluid which 

 exudes from the foot, than that the phenomenon which 

 he observed was an instance of moUuscan o-ropr^rj. 

 The shell represents part of a cone whose section is an 

 irregular ellipse. It is composed of three layers, as in 

 many other univalves. According to Carpenter the 

 inner and outer layers in Patella are rather less compact 

 than usual ; the middle layer is " composed of tolerably 

 regular polygonal cells, which form only a thin layer in 

 some parts, whilst in others they are elongated into 

 prisms.^^ 



