T. W. Engelmann on the Infusoria. 253 



nucleus, the preliminary stage in the formation of germinal cor- 

 puscles was observed taking place in the nucleus, and ending in 

 the production either of a very large number of small ones 

 closely packed and having a central vesicle, or else of a smaller 

 number imbedded within the substance of the nucleus. At the 

 same time, one, or, seldom, several elongated sharply outlined 

 bodies, having clear vesicles internally, were visible in the nu- 

 cleus ; and these after a while broke up into many smaller seg- 

 ments. Within other nuclei one or more extended, sharply 

 defined, homogeneous masses, of firmer consistence than the 

 nuclei themselves, were detected, but no spherical corpuscles. 



The somewhat reniform corpuscles remarked by Claparede 

 scattered in pairs through the parenchyma of Epistylis flavicans 

 appear to be peculiar to this animalcule. They strongly refract 

 light, and vary much in number, sometimes are absent alto- 

 gether. Their purpose is obscure. 



In Carchesium polypinum Engelmann observed the origin of 

 germs and embryonic corpuscles several times in May and Oc- 

 tober 1860. Usually only one globular germ appeared at a time, 

 close under the integument of the anterior portion of the body, 

 distinguishable by its clear homogeneous substance and its very 

 large central nucleus. At one point in its periphery a hollow 

 space, slowly changeable in its dimensioA (a contractile vesicle), 

 was also perceptible. The nucleus of the parent animal was 

 always present unchanged in appearance. 



In June 1860, Engelmann met with a specimen of Carchesium 

 polypinum having a thick bud-like outgrowth from near its stem, 

 gently tapering in front, with a circular opening at its apex. In 

 its interior were several rather large, strongly refracting corpus- 

 cles, of an oval figure, not dissimilar to germinal corpuscles. In 

 course of time this process collapsed, and hung like a flabby sac 

 from the Carchesium. Stein has recorded a similar formation in 

 Vorticella nebulifera. 



But it was in the Carchesium Aselli, a new species discovered 

 by himself, that Engelmann was enabled more fully to explore 

 the phenomena of embryonic development. On the 1st of April, 

 1860, he met with a full-grown dead specimen of this species, 

 containing a large spherical homogeneous body, 0*042 milli- 

 metre in diameter, possessing a round nucleus of considerable 

 magnitude. Contiguous to it lay the smaller, curved, horse- 

 shoe-shaped nucleus of the animalcule. On the following day, 

 he saw eight examples, each containing one such embryonic 

 globule, which lay close beneath the peristome. A slowly con- 

 tractile vesicle existed on the surface of each ; and, by the addi- 

 tion of acetic acid, an opake distinctly defined nucleus was brought 

 into view. The nucleus of the parent being could not in all 



