ZOOLOGY AND BOTANY, MICROSCOPY, ETC 261 



various sizes and shapes. During the anaphase stages the several diverse 

 chromosomes at one end of the nucleus correspond to chromosomes of 

 the same size and form at the other end of the nucleus. There are no 

 massive chromosomes in the multinucleate species, but there are coarse 

 chromatin masses. 



The granular chromosomes consist "of lines of granules which are 

 hardly larger, but stain more deeply, than the achromatic granules. 

 The multinucleate and binucleate forms take equal and very similar 

 care of the granular chromatin in mitosis, but they differ greatly in the 

 attention paid to the massive chromatin in the division of the nuclei. 

 The binucleate forms manipulate the chromatin masses as carefully as 

 the granular chromosomes, dividing and distributing them as accurately, 

 and retaining among them the characteristic diverse forms and sizes 

 always recognizable in the massive chromosomes during the anaphases of 

 mitosis. The multinucleate species, on the other hand, neglect the 

 chromatin masses, making no provision for their division or for the 

 presence of even approximately ecpial quantities of massive chromatin 

 in the two daughter nuclei. In spring, in both the multinucleate and 

 binucleate species, all the massive chromatin is thrown away, the 

 granular chromosomes become more compact, and growth processes are 

 at a low ebb, until the readjustments resulting from the sexual process 

 are accomplished. Then new massive chromatin is formed from the 

 granular chromatin, much as in Paramecium the trophic macronucleus 

 arises from an originaly idiochromatic micronucleus. The difference in 

 the care exercised by binucleate and multinucleate species in dividing 

 the trophic massive chromatin is probably due to the less need for exact 

 equivalence of trophic qualities between the nuclei of forms which for 

 all but a week or so in the year live in a multinucleate condition. 



Infusorian Parasitic on Fresh-water Medusoid.* — G. Arnold and 

 C. L. Boulenger report that a peritrichous Infusorian of the genus 

 Trichodina was found in great abundance on the fresh- water Medusoid, 

 Limnocnida rhodesise Boulenger, from the Xorquane River. It occurred 

 not only on the manubrium, but also on the velum, the tentacles, and 

 the surface of the umbrella, sometimes in such numbers as to give the 

 whole Medusoid a spotted appearance when viewed under the lens. 

 Some were found inside the circular canal, and showed no signs of 

 having been acted on by digestive juices. This suggests that Trichodina 

 is able to lead an endoparasitic existence within the gastrovascular 

 system. The Infusorian occurs also on L. indica and L. tanganicse, so 

 that it seems to be a common associate of fresh-water Medusoids, and 

 must play much the same role with regard to these organisms as it does 

 in the case of the species of Hydra in Britain. 



Scissiparity in Peridinidse.f — M. Pavillard discusses the phenomena 

 of growth and scissiparity in the genus Phalacroma. Alongside of the 

 normal individuals there are individuals of large size, and with inclusions 

 which may lie nutritive reserves. The increase in size is clue to the 



* Proc. Zcol. Soc, London, 1915, p. 75. 



t Coinptes Eendus, clx. (1915) pp. 372-5 (2 figs.) 



