INYERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 745 



systems " in its neighboiirhoorl are very commonly filled with dolomite, 

 instead of witli serpentine ; (2) in one and the same canal-system, 

 some of the branches are often filled with dolomite, and others with 

 serpentine ; while (3) individual branches are often partly filled with 

 one mineral and partly with the other. 



How these facts can be explained, except by the pre-existence of a 

 system of canals in the calcareous layers into which these minerals 

 have penetrated, he is unable to conceive ; and that they thus afford 

 demonstrative evidence of a structure which cannot be otherwise than 

 organic is not merely his own opinion, but that of Professor Geikie, 

 who has been for some years engaged in the microscopic study of the 

 metamorphic rocks of Scotland, and Professor Bonney, who has been 

 similarly studying the Cornish serpentines. 



Whether, when taken in connection with the general structure of 

 the organism, these "canal-systems" indicate its Foraminiferal affinities 

 is, of course, an altogether different matter. To Professor Mobius 

 the difference seems greater than the resemblance ; but it is note- 

 worthy that his comparisons are limited to tyjjes examined by himself, 

 and do not extend to Calcarina, in whose " canal-system " Dr. Dawson 

 and the writer recognize the nearest approach to that of Eozoon. He 

 cannot regard it as a valid argument against its Foraminiferal affinities 

 that its canal-system has a plan of its own. 



That in its general plan of growth (to which the distribution of the 

 canal-system is intimately related) Eozoon differs from all recent 

 Foraminifera at present known cannot be regarded as a proof of its 

 non-foraminiferal character by any who have fully studied the very 

 wide range of forms which that group comprehends, including the 

 numerous indefinite "arenaceous" types, whose import is only now 

 beginning to be understood by those who have the best opportunities 

 of studying them. He finds in the chambered structure of Eozoon, 

 and in its general relations to the canal-system traversing its cal- 

 careous layers, points of essential conformity to the Foraminifera, 

 which far outweigh the differences of detail by which Professor 

 Mobius has been led to the opposite conclusion. 



Hereafter he proposes to show that the " cumulative" argument in 

 favour of the organic character of Eozoon is as strong as that of the 

 human origin of the " flint instruments." Any one of the fractures 

 that has given to these their characteristic forms, might have been 

 accidental ; and yet it is impossible to conceive that any number of 

 such flints can have been so shaped " by accident." 



Peridinium and Gymnodinium.* — Dr. Q. Joseph, in describing 

 the " Grotten-Infusorien," gives a valuable account of the history of 

 the cilio-flagellate forms which have been known under these two 

 generic names. 



The Peridinia of fresh water are distinguished by a differentia- 

 tion of the outer layer of their body-substance, which takes on the 

 form of a smooth or a plated carapace. The oval body is convex 

 on its dorsal, and more or less flat on its ventral surface. The 



* 'Zool. Anzeiger,' ii. (1879) p. 114. 



