Their Collection and Investigation. 53 



relative length of these appendages in the flagellate class 

 is of high importance, but is ascertainable in many cases 

 only in connection with a prolonged and careful examination. 

 The manner in which food is ingested by the Flagellata, 

 whether by a distinct mouth or through the general surface 

 of the body, should be accurately determined. Sucli obser- 

 vation may be greatly facilitated by the addition to the water 

 of a little carmine or other pigment from an ordinary box of 

 water-colours.* Special attention should be bestowed upon 

 the reproductive phenomena. All Infusoria multiply rapidly 

 by simple subdivision or fission, and it should be noted 

 whether this fissive process takes a longitudinal, transverse, 

 or obhque direction. Some forms give birth to living 

 embryos, while among the Flagellata it generally happens 

 that the whole body-mass splits up into spore-like elements. 

 Sometimes this reproductive process is preceded by the 

 fusion or conjugation of two or more animalcules. It should 

 be the object of the investigator to ascertain and register as 

 many data as possible connected with these several phenomena. 



* [Until the last few years it was thought impossible to preserve most of 

 the Infusoria for future study and reference, but Mr. Kent has elsewhere 

 described {' Manual of Infusoria,' p. 113) the value of osmic acid as an 

 agent for their conservation. A drop of the solution in distilled water 

 (1 per cent, solution) should be placed on the covering glass before the 

 latter is placed over the specimen. All structures, such as ciha, cirri 

 and flagella, the internal endoplast, and in Euglenia and its allies, the 

 colours also, are stated by Mr. Kent to be perfectly preserved. The 

 animalcules thus killed may be fastened down as permanent preparations, 

 without the addition of any other preservatives, and may be stained with 

 the ordinary agents, haematoxylin, eosin, picro-carmine, &c., known to 

 histologists. The objection to osmic acid is that it is very costly and 

 excessively poisonous, its vapour having an intolerable odour, and 

 attacking the eyes in a very painful manner. A solution of iodine in 

 potassium iodide is without these objections, and acts in a similar, and 

 almost equally efficient, manner. Another harmless agent is afforded, 

 according to M. du Plessis, by a saturated solution of potassium perman- 

 ganate ; and for the preservation of the stalked Vorticellida very dilute 

 spirit (1 in 10) is recommended. For manipulative details the student 

 may usefully consult Huxley and Martin's ' Practical Biology,' Carpenter 

 and Beale on the microscope, and Schaffer's 'Practical Histology,' in 

 addition to Mr. Kent's majjiium upus, above cited. — Ed.] 



