ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 635 



mentation, not as a result of starvation, but at the beginning of a 

 decline in the nutritive conditions, after a period of exceptional richness 

 that bad induced rapid multiplication. At the time of conjugation the 

 animals are often in good condition, and multiplication may still be in 

 progress. In the races conjugating less readily the external conditions 

 favouring conjugation are probably somewhat different yet of a similar 

 general character. The differences in different races in the matter of 

 conjugation do not bear a simple relation to the relative size of other 

 morphological characteristics of the race. The two largest and the two 

 smallest races observed conjugated only rarely ; the race that conjugates 

 most frequently is intermediate in size. Among the races that conjugate 

 rarely are some with two micro-nuclei and some with one. The fact 

 that, in a given race, conjugation may be repeated (in the same line of 

 descent) at intervals of five days to a month, and the fact that races 

 derived from a single individual may live without degeneration for three 

 years without admixture from outside, tend, along with the results of 

 Woodruff, Enriques, and others, to weaken the theory that conjugation 

 is to be considered as a result of senile degeneration at the end of the 

 life-cycle. 



Nuclear Changes in Conjugation of Colpidium.* — A. Dehorne finds 

 that in Colpidium colpoda the process of conjugation is similar to that 

 which he has described in Paramecium caudatum. When the migratory 

 micro-nucleus is about to cross over, the stationary nucleus moves farther 

 back and becomes appressed to the macron ucleus, within a vacuole in 

 which it degenerates. The micronucleus which has passed over elongates 

 and forms a spindle, but the stationary nucleus disappears. The long 

 spindle, extending posteriorly, completes its mitosis and forms two micro- 

 nuclei, which immediately prepare for another mitosis. 



New Species of Mesnilella.f — E. Andre describes from the alimentary 

 canal of the Oligochget Lumbriculus variegatus a new species of this 

 genus of astomatous Ciliata. He names it Mesnilella cepedei sp. n., and 

 distinguishes it from other species mainly by the shape of the supporting 

 " spiculum," which runs out into a thread posteriorly and by the number 

 (1-4) of contractile vacuoles. 



Internal Euglenid Parasite. $— P. de Beauchamp describes Astasia 

 captiva sp. n., which he found very active and in large numbers inside 

 the chain-forming Turbellarian Gatenula lemnse. It has no chlorophyll 

 nor stigma, but its position is indubitable. A case of parasitism among 

 Euglenids may possibly have some interest, the author suggests, in con- 

 nexion with the much-debated question of the origin of Gregarines. 



* Comptes Rendus, clii. (1911) pp. 1354-7 (9 figs.). 

 + Rev. Suisse Zool., xix. (1911) pp. 2G7-70 (1 fig.). 

 % Arch. Zool. Exper., v. (1910) Notes et Revue, No. 5, pp. lii-lviii (2 figs.). 



