274 GENERAL HISTOEY OF THi; IIM L.-SOlcIA. 



sented one, and also the possible admission of coloured food, but was contra- 

 dicted by Dujardin, who denied both. Siebold reckons Peiidinicea among 

 mouthless Infusoria {Astoma). Perty mentions the fossa in the shell, but no 

 aperture ; and Allman remains silent on the matter. On the other hand, Lach- 

 mann admits its presence, and thus discusses the mode of reception of food 

 (J..iV^.ir.l857, vol. xix. p. 220) :— "Prom the point of insertion of the flagel- 

 lum, on one side the large notch, in the upper part of the row of cilia, a clear 

 canal passes into the body of the animal, and dilates at the extremity to form 

 a cavity of variable diameter. The flagellum is often seen to contract rapidly 

 into a spiral form, and apparently disappear ; and not unfrequently we may 

 then succeed in perceiving that it is jerked back into the above-mentioned 

 cavity, from which it soon retui^ns into its previous position. Now it cer- 

 tainly appears worth while to see whether small particles of food are not 

 carried into the cavity by this jerking in of the flagellum." 



Contents. — These may be divided, as in the Euglence, into minute shapeless 

 molecules, and globular corpuscles and vesicles with red stigma and nucleus. 

 Sometimes the corpuscles are green, and resemble chlorophyll, but more fre- 

 quently they are red, yellow, or brown, or intermixtui'es of those colours. In 

 the earliest stages, indeed, colour is absent, and, just as in Euglencea, only 

 minute moleculse are found interspersed in the colourless protoplasm. More- 

 over, when a colour appears, it may not simply become more intense or darker 

 by age, but change to another tint belonging to the same series of colours. 



In younger specimens again, the contents more completely occupy the 

 entire being, whilst frequently in old, and more especially in specimens 

 withering or dying, they become contracted into a ball, placed either in the 

 centre or more or less to one side (excentric). A swelling out of the external 

 tunic, the disappearance of the red stigma, the vibratile cilia, and the filament 

 accompany this shrinking of the cell- contents. The retrograde change in 

 the contents is further manifested by the appearance of a large vesicle about 

 the centre, or of several dispersed smaller ones at that or in other parts. 

 Some at least of these vesicles are merely oil- drops, which, as Braun shows 

 in his essay on Rejuvenescence, are the usual concomitants of a process of 

 destructive assimilation. After the destruction of the cell- contents, the firm 

 lorica remains hke an empty shell, boldly displaying its sculpturing, and in 

 many instances also a curved, apparently internal, stripe about the middle or 

 to the right of it, which Perty presumes to be either the Line of attachment 

 of the contents or a fold. 



Among more constant structures. Dr. Allman describes a central nucleus — 

 the organ probably alluded to by Ehrenberg under the name of an oval semi- 

 nal gland, in Peridinium Trij>os and P. Fusus. AUman describes the nucleus 

 to be of an irregular oval form, quite colomiess, and marked on the surface 

 with curved striee (XXXI. 20) ; under pressure the envelope gives way, and 

 the nucleus escapes with the other contents. A contractile vesicle has not 

 hitherto been discovered. One or more large clear vacuoles may originate in the 

 internal substance ; but such have not the pulsating power of definite vesicles. 



The red speck or stigma (XXXI. 16, 17) has no pretensions to the nature 

 of a visual organ. It is not always present even in examples of the same 

 species ; or it is multiplied ; and it is known also to disappear v^ith advancing 

 age. Again, Perty recounts the fact of the diflPiision of the red colour 

 of the speck throughout the whole contents, at times leaving a narrow ex- 

 ternal ring w^hich retains its green colour. This phenomenon was witnessed 

 in a specimen of Olenodinium cinctum. In young individuals of Peridinium 

 tahidatum, which are of a light-green colour and translucent, there is no trace 

 of a red speck ; yet Perty met with a collection of these beings of apparently 



