862 APPENDIX. 



exhibit a trace of contractility like dying cilia. Numerous observations have con- 

 vinced Mr. Geddes that these cells are really parasites. Other species of Planarians 

 yield nothing like them. The delicacy of their protoplasm distinguishes them from 

 the true tissue of the Convoluta. Moreover, they do not form tissue, and have no 

 definite disposition. Regarded as parasites, their structure, apparently so abnormal, 

 is readily derived from the type of ordinary Infusoria by the suppression of the cilia, 

 which would not be available for locomotion among the cells of the mesoderm, and 

 the differentiation of the contractile vesicle. This differentiation of the vacuole is 

 remarkable with reference to its relative enormous proportions, the development of 

 contractile fibres which limit it, and the rapidity of its contraction. Being altogether 

 distinct from the ordinary Flagellate, Ciliate, and Suctorial (Tentaculiferous) sections 

 of the Infusoria, its discoverer proposed to establish a new sub-class, the Pulsatoria, 

 for its reception. 



GENERAL HISTOLOGY AND PHYSIOLOGY. 



Fertilization of Seaweeds by Infusoria. 



The very interesting discovery has been made by Dr. Dodel-Port, of Zurich, * that 

 Infusoria, Vorticelte, are instrumental to a large extent in the fertilization of certain 

 Floridaceous Alg^e. In Polysiphonia subulata the antherozoids, produced from 

 antheridia on separate plants, are of a simple spheroidal form and possess no cilia 

 or other locomotive organs. Their union with the reproductive structures or carpo- 

 gonia of the female plants, which would be otherwise very hazardous, is greatly 

 facilitated by the usual presence upon the fruit-bearing branches of numerous 

 Vorticellae. The characteristic ciliary currents produced by these animalcules attract 

 the antherozoids floating in the neighbourhood, and cause some one or more to 

 strike upon and adhere to the trichogyne or slender tubular hair which is produced 

 from the distal region of the carpogonium, and which subserves the purpose of the 

 pistil in an ordinary flowering plant. In this manner fertilization is effected by a 

 process closely analogous to what obtains among the wind-fertilized or so-called 

 " anemophilous " dioecious phanerogams. 



Muscle or Nerve-fibres in Siylonychia 7nytilits. 



T. W. Engelmann "f remarks of the above-named Infusorian that it unquestion- 

 ably possesses a system of ventral fibres trending from near the middle line, beneath 

 the ectoplasm, to the two conspicuous series of large admarginal cilia which so 

 powerfully aid in the motions of this animalcule. These fibres are not like the 

 fibres of ordinary ciliated cells, nor are the lashes which diey supply cilia properly 

 so called. The lashes (cirri) are complex appendages remote from one another, 

 moving independently under the control of their possessor. Each has its own fibre, 

 which is pale, soft, and homogeneous. The fibres are parallel, and so delicate that 

 they can only be seen for a short time in specimens starved during some hours in 

 filtered water and then killed in osmic acid. Their interpretation as true nerve- 

 fibres is favourably entertained by Engelmann. 



Method for Colouring Infusoria during Life. 



M. A. Certes % finds that Infusoria placed in a weak solution of chinolin or 

 cyanine — proportion from i to 500,000 and not exceeding i to 100,000 of ordinary 

 filtered water — are coloured a pale blue, and may contmue to live for as long as 

 thirty-six hours. The coloration is concentrated round the fat-granules of the 

 protoplasm, but affects feebly or leaves altogether untouched the cilia, cuticle, 

 nucleus, nucleolus, and vacuoles. The colour disappears on long exposure to light 

 or if the objects are mounted in glycerine. 



* 'Kosmos,' 1879; also 'Nature,' No. 515, Sept. 11, 1879. 

 t " Pfliiger's Aichiv Physiologic," Bd. xxiii., 1880. 

 X ' Comptes Kendus,' xci., 1881. 



