ZOOLOGY AND BOTANY. MICROSCOPY. ETC. 767 



Method of Demonstrating Presence of Uric Acid in Contractile 

 Vacuoles of lower Organisms.* — Dr. A. B. GriflSths has been able, by 

 direct experiment, to show that' at certain times the contractile vacuole 

 of tlie Prot )Zoa performs the fxmction of a true kiclne7. A nnmber of 

 Amoehse were placed on a microscopic slide and covered by a thin glass 

 slip ; alcohol was run in to kill them, and was followed by nitric acid. 

 The slide was gently warmed and ammonia introduced. In a few 

 minutes prismatic crystals of murcxide, having a beautiful reddish- 

 purple colour, made their appearance. Similar results were obtained 

 with Vorticella and Paramsecium. 



Symbiosis of Algae and Animals.f — Prof, A. Famintzin states that 

 the Alga with wh'ch Tintinnus inquilinns is symbiotic, is not, as 

 previously supposed, an Ectocarpns, but a diatom belonging to the genus 

 Chsetoceros. It unites itself with a 1-5-celleil colony of the diatom, 

 its envelope becoming completely welded with it. When the union takes 

 place at an early stage, the horns of the diatom fre(|nently fail to 

 develope. 



The yellow cells of the Radiolaria are identified by the author with 

 Zooxantliella extracapsularis and intracapsidaris, the former only of which 

 is known to develope outside the host. In opposition to the statement 

 of Brandt, the autlaor finds that tlie Kadiolaria, especially Collozoum 

 inerme and S'phserozoum punctatiim, live on the yellow cells not only 

 immediately before the foimation of the spores, but at all times, im- 

 parting to them their golden yollovv or rusty brown colour; and the 

 same is the case also with several Actiniae. 



Holotrichous Infusoria.^— In the introduction to his description of 

 some Holotrichous Infusoria, Dr. W. Schewiakoff defines certain terms 

 which he uses. Very small forms are those which do not measure more 

 than 0-04mm. ; small, those not more than 0-07 mm.; of medium size, 

 those less than 0-12 mm.; the large are not more than 0*25 mm., and 

 very large those that are more. But these definitions are, of course, 

 conventional. Stifi" Infusoria are those whose bodies undergo no altera- 

 tion in form ; elastic those which do not change of themselves but are 

 altered in consequence of some external pressure, on the cessation of 

 which they return to their former form. Flexible Infusoria have the 

 power of independently altering without making any noticeable change 

 in their general form ; while contractile Infusoria are those which can 

 lengthen or shorten one dimension at the expense of others, and are, 

 consequently, able to alter their form very considerably ; in such cases 

 special contractile elements are generally present. 



The ectoplasm of Infusoria has generally the appearance of a thin, 

 sharply limited layer of protoplasm, which is distinguished from the rest 

 by its greater density and its higher refractive power ; it is either homo- 

 geneous or has the si)ecial alveolar structure first described by Biitschli. 

 The name of pellicula is suggested in place of the ordinary term cuticula, 

 as this bounding lamella is not a dead secretory product, but merely a 

 metamorijhosis-product of the protoplasm. Between the alveolar layer 

 and the endophism a specially differentiated layer can, in some cases, be 

 distinguished, and for this we may well use Biitschli's name of cortical 



* Proc. R. Soc. Ediub., xvi. (1888-9) pp. 131-.5. 



t Mem. Acad. Imp. St. Pe'tersbnurji:, xxxvi. (1889) 36 pp. and 2 i)1h 



X Bibliotlieoa Znolog., v. (1889) 78 pp. (7 pin.). 



