194 Teratology of Infusoria. {']XX ZrnHm' 



will give a direct motion in the microscope from right to left when 

 the object is moved from right to left. As an encouraging practising 

 to those who desire to accomplish this microscopical feat for them- 

 selves, I beg to recommend the prehminary use of weU-mounted 

 Beetles-eyes, in which the images can be well studied. Precisely- 

 analogous effects in every respect may be looked for, in the convex 

 spherical refracting surfaces of diatoms. "When the lens is concave 

 or double concave, the image I find by calculation lies beneath the 

 ordinary surface. 



VII. — A Contribution to the Teratology of Infusoria. 



By J. G. Tatem. 



Plates XLVII. and XLVIII.. 



It is sufficiently well known that the ciliated Infusoria, under hke 

 phases of existence, maintain in each species a definite and constant 

 outline, and that differences of size or of colour, consequent on the 

 injection of food varying in quantity and character, are all which 

 distinguish one individual from another. These precise and fixed 

 forms are, however, occasionally, though rarely, departed from ; 

 and we meet with examples of malformation, dependent in these, as 

 in all other such cases, on hypertrophy or on arrest of development. 

 Of the few such instances as have from time to time come under my 

 observation I made careful drawings, and these I now beg to submit 

 to your examination. 



In Fig. 1 we have a Traclielias anas, in which the lip, or brow 

 (as it is sometimes called), is inordinately prolonged, somewhat 

 spirally coiled, and clothed with longer and stouter ciha than 

 usual. 



In Figs. 2 and 3, a Chilodon cucuUulus, we have also a mon- 

 strous development of the same part, the hp projecting into an 

 elongated proboscis-like appendage, which, as seen waving to and 

 fro, and twisting with every movement of the animal, presented a 

 singularly grotesque appearance. 



In contrast with the two preceding is a charming Vorticella, 

 Fig. 4. Elegant and attractive as are the several species of VoHi- 

 cellse, it surpasses them all in beauty, and it is with reluctance only 

 that we can be brought to regard it as a monstrosity. Met with 

 on seveial occasions and in widely distant localities, we may fairly 

 question if it may not rather claim the importance of a named 

 variety, under that of Vorticella convaUaria, var. monilata. I have 

 always entertained the opinion, though unable to assure myself of 

 the fact, that the transverse striations on the body of Vorticella con- 



