ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 521 



on the genetic relationship of the Cilioflagellata and the Peritricha is 

 at present offered. 



Development and Classification of Polytoma, Ehr.*— J. Krassil- 

 stschik describes Polytoma spicatum which he found in the same in- 

 fusion f as P. uvella. It is distinguished from the latter by having 

 a body pointed behind, and it is somewhat more slender, being when 

 full-grown 20-25 /x by 10-12 fx as against 19-23 /x by 11-13 ^. 



The development of both species of Polytoma is as follows : — The 

 young passing from the resting stage divide into eight parts. This 

 division is at first into two, then into four, and finally into eight. It 

 extends throughout the whole body-substance within the envelope of 

 the mother organism. The latter, as well as its two flagella, remains 

 uninjured during the fission and their motion is not in the least dis- 

 turbed. The eight cells assume at first a round form, then elongate, 

 and take the shape of a Polytoma. After the bursting of the parent 

 envelope the eight young ones escape, and begin to grow until they 

 attain the size of a full-grown Polytoma. Then they also divide in 

 the same way as tlje earlier ones, but this time into four, and never 

 into eight parts. The division into eight is not again met with, since 

 each succeeding generation divides into four and only four, pro- 

 vided that there is no considerable alteration in the temperature, 

 nourishment, or life-conditions of the Polytoma. In from four to 

 six days most of the individuals commence to conjugate in pairs, form 

 zygotes, assume a spherical form, and after the secretion of a tolerably 

 thick membrane pass again into the resting condition. During the 

 fusion of the two zoospores, the nuclei also blend together. The 

 conjugating Polytoma vary very little, if at all, from the non-conju- 

 gating. The last generation are mostly distinguished by the size 

 and bright colour of their starch-containing granules. This, how- 

 ever, is not always to be relied on, as wdth rich nourishment all 

 have somewhat large, bluish-green corpuscles, and in unfavoui'able 

 circumstances even the conjugating individuals have only small pale 

 granules. The size also to which the latter attain is not always the 

 same. For the most part the young do not begin to pair immediately 

 after their exit from the parent envelope, but grow somewhat first. 

 Moreover, when they have not the opportunity to pair whilst still 

 small, they continue growing to the size of a full-grown Polytoma, 

 and still retain their capacity for conjugating. These can pair either 

 with each other or with quite young Polytoma. It is easy to under- 

 stand that where a full-grown conjugates with a young one, it seems 

 as if it was the conjugation of a macro- with a micro-zoospore, or a 

 male with a female. Exact observations on the development of 

 isolated examples of Polytoma have however showTi that there are 

 neither macro- nor micro-, male nor female zoospores to be distin- 

 giiished ; further, that there is no distinction between the Polytoma of 

 the last and the first generation, and that in certain circumstances the 



* Zool. Anzeig., v. (1882) pp. 426-9. 



t The infusion was made by moistening with water tlie muddy sediment 

 from a fountain basin. To this infusion rotting leaves were added and the 

 vessel set in a warm place. 



