ECONOMY OF THE DAPHNIA. 171 



bodies as eggs, thus following Sir John Lubbock's lead without 

 prejudice to the disputed point as to whether they are properly 

 entitled to the term, or can only be described as buds. Beside 

 this, reproduction is carried on by what is believed to be a true 

 sexual process, resulting in the production of ova which are des- 

 tined for a slower course of development, and for that purpose are 

 enclosed in a specialized portion of the brood-receptacle, called 

 the ephippium (Figs. 2, 24, and 28). I will first describe the 

 course of the agamic eggs, partly from Sir John Lubbock's obser- 

 vations, and partly from my own. The ovaries are placed on 

 either side of the alimentary canal, and contain, surrounded by a 

 cellular matrix, the bodies which Sir John calls ovarian masses 

 (Figs. 9 and 14). They each contain from two to four or five 

 cells, each with a large circular nucleus in the centre. Four or 

 five of these usually follow each other, and it appears that those 

 nearest the heart are earliest in their development. In course of 

 time, all but one of the nucleated cells disappear from the ovarian 

 masses. One, however, remains and becomes the germinal 

 vesicle. Dark granules and oil-globules (Fig. 15) collect around 

 it, and the yelk thus formed is of a greenish hue in all the speci- 

 mens of Daphia pulex which I have specially examined. When 

 one brood of young are on the point of passing from the recep- 

 tacle into the water to commence an independent fife, the ovary 

 may be seen filled with a mass of these ova ready to take their 

 places. 



It would be interesting to observe how the ova make their way 

 from the ovaries into the receptacle. Sir John Lubbock speaks 

 somewhat doubtfully of their passing out near the heart, and I 

 should think it probable that such is the case, inasmuch as the 

 more advanced eggs always appear to be in this situation, but I 

 have not, neither has Sir John, been able to detect any duct by 

 which they make the passage. The eggs, when they have passed 

 into the receptacle, are surrounded by a covering which Sir John 

 Lubbock describes as the vitelline membrane, and the contents 

 appear to me to be granules and small cells, having a large and 

 conspicuous oil-globule in the centre (see Fig. 23). Curiously 

 enough, the eggs are now of a reddish-yellow hue, at least, in 

 Dap/mia pulex, where alone I have particularly observed them, the 

 green hue subsequently again prevailing through the multiplication 

 of green cells, each containing an oil-globule. At this time, the 

 blastodermic layer is, I believe, in course of formation, but my 

 optical means will not allow me to speak with certainty on the 

 point. The green cells which Sir John Lubbock describes as 

 yelk-masses become larger and are aggregated round the large, 



