in Eudorina elegans and Cryptoglena. 241 



when their disappearance can only be accounted for by their 

 having become incorporated with the green cells. Eudorina in 

 this stage also may frequently be seen with all the four anterior 

 cells absent, and only a few spermatozoids left, most of which are 

 motionless and adherent to the capsules, — indicating that the rest 

 have disappeared in the way mentioned. Lastly, many Eudorina 

 in this stage may be observed with not only the four anterior 

 cells absent, but with hardly a single spermatozoid left, — indi- 

 cating that the whole had passed into the female cells, or had 

 become expended in the process of impregnation. T have never 

 seen any spermatozoids in the central or axial cavity (fig. 2 c), 

 nor do I think that there is a means of their escaping externally 

 without rupture ; so that their being confined to the space be- 

 tween the two ovoid cells of the Eudorina, where the green cells 

 are situated, is another reason, if any more be needed, for con- 

 sidering them fecundating agents. 



What changes take place in the Eudorina after this, I have 

 not been able to discover. At the time, the female cells appear 

 to become more opake by the incorporation of the spermatozoids, 

 and the crenulated state of the posterior part of the envelope in 

 this stage seems also to indicate an approach to disintegration. 

 I have also observed that those Eudorina which are undergoing, 

 or apparently have undergone impregnation, are less active than 

 the rest, — that is, those in which the spermatozoids are scattered 

 throughout the interspace mentioned and applying themselves 

 to the capsules of the green cells, and those in which there are 

 only a few spermatozoids left. But even if they did become dis- 

 integrated, the latter, when free, would so closely resemble those of 

 Chlamydococcus (fig. 9), which was also abundantly present, that 

 unless the Eudorina could be found undergoing impregnation 

 by itself, or apart from this organism, there appears to me no 

 chance of distinguishing the two, and therefore no other means 

 of completing this part of its history. It is true that the im- 

 pregnated cells may undergo some change in form similar to 

 those of Volvox globator after impregnation*; but I think I 

 should have seen this among the numbers which came under 

 my observation, if it had been the case. 



While undergoing impregnation, the female cells always con- 

 tain from two to four nuclei, as if preparatory to the third stage of 

 development (PI. VIII. figs. 3 h and 4 b), into which they are 

 sometimes actually seen passing, with the spermatozoids present 

 and scattered among them ; but the effect of impregnation ge- 

 nerally seems to arrest this stage, and thus save the species from 



* See Ehrenberg, tab. 4. figs. 2 & 3; also Busk, Quart, Journ, Micro- 

 scop, Soc. vol. i. p. 38 and pi. ; and Conn, I. c. 



