150 



Prof. M'Intosh's Notes from the 



Fiff. 1. 



Fiar. 2. 



A male measuring 3h inches in length presented in the 

 thickened generative region of the mantle large pale round 

 sperm-sacs filled with minute spermatozoa (fig. 1), which have 

 minute ovoid bodies with finely filamen- 

 tous tails. They are lively and tenacious 

 of life. Thus specimens examined at 

 11 a.m. were allowed to remain on the 

 slide till 1 p.m., at which period no move- 

 ment was discernible in the partially 

 dry preparation. On adding some of 

 the limpid fluid from an adjoining 

 mussel active motion was resumed. 

 The same was repeated at 4 p.m., with 

 a similar result. Twenty-four hours' 

 exposure, however, seemed to be fatal. 



The females had the same region of the mantle crowded 

 with a prodigious number of minute ova 

 (fig. 2). In shape these are ovoid, with a 

 transparent investment and an inner granular 

 yolk with a pale circular area. 



As the month (February) advanced the 

 mantle, especially in the neighbourhood of the 

 organ of Bojanus, increased considerably in 

 thickness, so that the region hung downward 

 like a pouch or flap on opening the valves. 

 The whole surface of the mantle becomes 

 speckled in both sexes with the reproductive elements. On 

 puncturing the enlarged region at the organ of Bojanus in a 

 male on the 17th February a milky fluid composed of sperms 

 exuded. The mantle in this case had increased in thickness 

 about three eighths of an inch, and the development of the 

 sperm-sacs seemed to proceed from the dorsal to the ventral 

 edge of the mantle. Even in specimens in which the shell has 

 been injured and the mantle remains thin at certain places an 

 immense number of ova are developed. 



After full maturity is attained, as in April, the orange 

 mantle is richly marked in an arborescent manner by racemose 

 sperm-sacs and ducts, especially towards the margin, and 

 when the mantle is swollen with water the sperm-sacs project 

 like bunches of grapes. In the female this appearance is not 

 so evident, for the ova are grouped in masses of a circular or 

 ovoid form and densely packed. 



About the middle of May the activity of the spermatozoa 

 seemed to be diminished, but the size and appearance of the 

 ova remained unchanged. On the 24th the sluggishness of 

 the spermatozoa was marked in most males, and certain sperm- 



