Reviews — Radiolarians, etc., in Pre- Cambrian Rocks. 419 



44 figured forms of which the dimensions are given is -0115 mm; 

 whilst the average diameter of 44 of the Palceozoic Radiolaria figured 

 by Dr. Eiist (talking the 44 species first described) is -2 mm. ; thus it 

 would require the combined diameters of 17 of the Pre-Cambrian 

 bodies to reach the average diameter of one of the Palteozoic Radiolaria. 

 The author considers that the small dimensions of the ancient forms 

 may possibly arise from different biological conditions, and, that as 

 size does not enter into the diagnosis of recent Radiolaria, the 

 objection is not valid in the present case. It may, however, be 

 noted that there is no important difference in the size of existing 

 Radiolaria and that of fossil forms as far down as the Silurian and 

 Ordovician rocks, and there is, therefore, no ground for anticipating 

 that still earlier forms would be more diminutive than those of 

 Ordovician and later times. Other objections are based on the fact 

 that it is only in some of these bodies that perforations can be 

 discovered, whilst it is also stated that they are too regularly 

 spherical to be Radiolaria, and further that the bodies are not organic 

 but are produced by the juxtaposition of small rounded granules, 

 and that the interstices between these give the appearance of perfor- 

 ations. The author considei's that such an interpretation is incon- 

 sistent with the law of optics, and that the perforations are really 

 pores in the siliceous test. 



Dr. Riist, judging from the section supplied to him by the author, 

 considered that the small rounded bodies more nearly resembled 

 the detached chambers of Foraminifera than Radiolaria, thus allowing 

 the organic character of the forms present ; bat this view does not 

 account for the larger perforations in the test of some, and further 

 will not apply to those which are bell-shaped. The author has, 

 however, since the publication of the first paper, communicated a 

 note to the "Comptes Rendus," in which he asserts the Foraminiferal 

 character of some of the bodies in the Pre-Cambrian phtanites 

 associated together with the forms described as Radiolaria. Of 

 these Foraminifera, both simple and compound forms are present, 

 but the simple specimens are hardly to be distinguished from those 

 Radiolaria in which the pores are obliterated. The compound forms 

 consist of a variable number — ranging from 2 to 7 — of spherical or 

 ovoid chambers of dififei-ent sizes aggregated together. In some 

 cases the chambers are furnished with one or more short blunted 

 spines. The walls are very finely perforate, and they are therefore 

 included in the perforate group of Carpenter. In. size they corre- 

 spond with the Radiolarian bodies ; the largest of the chambers hardly 

 reaching the diameter of 10 micromillimetres(=:-01 mm. or about 

 2 6-0 of an inch), and thus the objection made to the Radiolarian 

 bodies on account of the disparity in size in comparison with recent 

 forms will equally apply to these Foraminifera. 



The imjDortance of determining the real character of the minute 

 bodies in these Pre-Cambrian rocks will be generally recognised, 

 and we cordially trust the author will persevere in his researches 

 until he meets with evidence sufficient to convince those who now 

 feel some hesitation in accepting his conclusions about them. 



G. J. H. 



