12 D. MOORE ON THE GENERATIVE PROCESSES 



bient water or in the cavity of the mantle, or in that of the 

 outer gill, or in the cloacal space, or in the few viviparous species, 

 Kellia, Galeomma, Montacuta, within the ovary itself." This 

 evidently indicates a change of opinion among naturalists within 

 the last 20 years with regard to one, at least, of the creatures I 

 wish to draw your attention to. Professor Owen distinctly assert- 

 ing that the oyster has two sexes, Professor Rolleston, 20 years 

 after, as distinctly stating that the sexes are united in one 

 individual. I have been led by the facts I have observed 

 to think that the cockle and mussel ought also to be 

 classed as having the sexes united in one individual. The plan 

 I adopted in studying the subject was to examine a few of these 

 creatures week by week, knowing that I was more likely to 

 thoroughly master one or two at a time, and thinking that as the 

 breeding season approached I was sure to see individuals exhibit- 

 ing characteristic phenomena. I was indebted to the great kindness 

 of Mr. Fell Woods, the managing director of the South of 

 England Oyster Company, for a weekly parcel of oysters and 

 cockles. The mussels I received week by week from friends at 

 Hastings. 



The generative gland in the cockle is a somewhat loosely 

 attached, racemose structure, with its principal mass at the base of 

 the foot, but ramifying freely among the intestines and throughout 

 the muscular structure of the foot. The gland thus distributed is 

 made up of a vast number of lobules, connected together by stalks ; 

 roughly it may be compared to a very large bunch of grapes, or 

 many bunches united together by a common stalk ; the stalk 

 varying according to the state of gland, being either a delicate 

 transparent thread, or a convoluted mass of tubes, and the lobules 

 or grapes either containing spermatozoa in all stages, or 

 spermatozoa and clear cells, or eggs in various stages of perfection. 

 An isolated lobule appears to be composed of two membranous 

 sacs, one within the other; when spermatozoa are present 

 they are found between the outer and the inner sac; when 

 eggs are present they are found to be attached by their 

 micropyle to the circumference of the inner sac, and when hatched 

 the young find their way into the tubular structure, which appears 

 to be continuous with the outer sac. The tubular structure, when 

 full of young, appears muscular, and exhibits faint indications of 

 striation, and when ruptured forcibly expels its contents. The 



