GENERATIVE PROCESS IN PARAMECIUM. 465 



commencement of its resolution into separate ova ; while the 

 Seminal capsule is found to have undergone division into two or 

 four secondary capsules, b, b, each of which contains a bundle of 

 Spermatozoa now straightened out. This division takes place by 

 the elongation of the capsule into the form represented in fig. 11, 

 and by the narrowing of the central portion whilst the extremities 

 enlarge; the further multiplication being effected by the repetition 

 of the same process of elongation and fission. In fig. 3, which 

 represents one of the individuals still in conjugation, the four 

 Seminal capsules, b, b, are represented as thus elongated in pre- 

 paration for another subdivision; whilst the Ovary, a, a, has begun 

 as it were to unroll itself, and to break-up into fragments which 

 are connected by the tube m. In this condition it is that the 

 object of the conjugation appears to be effected by the passage 

 of the seminal capsules of each individual, previously to their 

 complete maturation, into the body of the other. In fig. 4 is 

 shown the condition of a Paramecium ten hours after the con- 

 clusion of the conjugation; the Ovary has here completely broken 

 up into separate granular masses, of which some, a, a, remain 

 unchanged, whilst others, o, o, o, o, either two, four, or eight in 

 number, are converted into Ovules that appear to be fertilized by 

 the escape of the Spermatozoa from the seminal capsules, these 

 being now seen in process of withering. Finally, in fig. 5, which 

 represents a Paramecium three days after the completion of the 

 conjugation, are seen four complete Ova, o, o, o, o, within the 

 connecting tube, m, m ,• whilst the seminal capsules have now 

 altogether disappeared. In figs. 13-18 are seen the successive 

 stages of the development of the ovule, which seems at first 

 (fig. 13) to consist of a germ-cell having within it a secondary cell 

 containing minute granules, which is to become the ' vitelline 

 vesicle.' This secondary cell augments in size, and becomes more 

 and more opaque from the increase of its granular contents (figs. 14, 

 15, 16), forming the ' vitellus' or yolk; in the midst of which is 

 seen the clear 'germinal vesicle,' which shows on its wall, as the 

 ovule approaches maturity, the 'germinal spot' (fig. 17). The 

 germinal vesicle is subsequently concealed (fig. 18) by the increase 

 in the quantity and opacity of the vitelline granules. The 

 fertilized ova seem to be expelled by the gradual shortening of the 

 tube that contains them ; and this shortening also brings together 

 the scattered fragments of the granular substance of the original 

 ovarium, so as to form a mass resembling that shown in fig. 1, a, 

 by the evolution of which after the same fashion another brood of 

 ova may be produced. The development of the ova after their 

 extrusion from the body has not yet been followed out ; and its 

 history constitutes a most important object of inquiry. 



348. The Reproductive process in the ordinary Infusoria was 

 entirely misconceived by Prof. Stein, who advanced the doctrine 

 that they commonly pass through the condition of Acinetce, which 



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