414 SUMMARY OF OUBKENT RESEARCHES RELATING TO 



Observations on Fresh-water Sponges.* — Dr. A. Wierzejski has somo 

 various notes on fresh-water sponges. He thinks that Herr Noll is wrong 

 in his account of the development of gemmulae-balls of Spongia fragilis ; 

 they do not develope from extraordinarily large rudiments by division 

 within the cellular cortical layer, but from special rudiments which the 

 author has already described. 



With reference to Dr. Vejdovsky's limitation of the hitherto known 

 Spongillidfe to eight species, pleas are put forward against Euspongilla 

 rhenana Retzer, and in favour of Ephydatia miilleri for which he thinks a 

 special place ought to bo found. 



Protozoa. 



Reticulated Structure of Protozoa.f — M. J. Kunstler calls attention 

 to a communication of his in 1881 in which he describes the structure of 

 protoplasm as alveolar. Without excluding strictly reticulated structure, 

 numerous observations go to show that vacuolar or alveolar is in many 

 cases the more accurate description. Ho notes the various modifications 

 of these alveoli. 



In Dumoniia apheliarum the vacuolar elements are aggregated in a 

 continuous mass, and do not separate into secondary groups. The small 

 peripheral alveoli which are not disposed in very regular layers, enlarge 

 towards the interior, and form a network with polygonal meshes. An 

 areolar structure of a similar character is seen in the internal protoplasm 

 of some Gregarines. The vacuoles contain fine granules. The circulating 

 food-vacuoles are then discussed. According to the author they are 

 surrounded by a proteid layer, formed at the mouth, and constituting 

 transitory but coherent stomachs. In the Cryptomonads these are re- 

 placed by a permanent cul-de-sac. Even the flagella exhibit an alveolar 

 structure. 



Reticular Structure of Protoplasm of Infusoria. X — M. Fabre- 

 Domergue recommends the following method of demonstrating the fine 

 reticulation of the protoplasm of Paramsecium, Vorticella, and other in- 

 fusorians. They are fixed by a weak solution of iodine, washed with 10 per 

 cent, solution of potash, and then with distilled water ; a drop of very dilute 

 'acetic acid is afterwards added. After coloration with eosin the proto- 

 plasmic trabeculsB are seen with the greatest distinctness. They are very 

 loose at the centre of the body, but more close in the ectosarc, where, as 

 in Opalina, Paramsecium is vacuolated. The viscosity of the protoplasm 

 is shown to be in relation to the condensation of the reticulum. This last 

 represents the fixed part of the protoplasm, and it is by the differentiation 

 of its substance at a given point that the contractile vesicle is formed. 

 The passage of food along a straight line in Didinium nasutum is likewise 

 due to the physiological differentiation of this reticulum. A distinction 

 must be made between infusorians in which there is a structural peripheral 

 reticulum and those which possess in addition an isolable cuticular 

 membrane. This latter must not be confounded under the generic term 

 of integument ; the Oxytrichidfe, notwithstanding their cuirass-like 

 ectoplasm, are really naked Infusoria. 



Multiplication of Ciliated Infu3orians.§— According to M. E. Maupas 

 (a) the reproductive power of Ciliata depends on (1) the quality and 

 quantity of food, (2) the temperature, and (3) the alimentary adaptation of 



* Zool. Auzeig., x. (1887) pp. 122-6. 



t Coinptfs Kuiidud, civ. (1S87) pp. 1009-11. 



X Ibid, pp. V'JT-O. § Ibid., jip. lOOG-8. 



