102 



HARDWICKE'S SCIENCE-GOSSIP. 



The genealogy you will see below, where from the 

 same root is shown the development of the rhino- 

 ceroses and tapirs on the one hand, and the 

 Macrauchenidce (a fossil genus for those animals 

 which exhibit a combination of the characteristics of 

 the horse, rhinoceros, and camel) on the other hand. 



Rhinoceroses Tapirs 



Horses 



Hipparion 



Macrauchenida 



Anchitherium 



alaeotheridse 



Now a small hoof with a supplemental digit in 

 our modern horse has been observed more than once ; 

 but the most instructive case is one recorded and 

 figured by Marsh in a paper on "Horses Recent 

 and Extinct," printed in the "American Journal of 

 Science and Art " for 1879, where the eight hoofed 

 Cuban pony had, in this one instance, a supple- 

 mental digit on the inner side of each limb (Fig. 46). 

 This pony was being exhibited as a marvel-wonder 

 in the States, and had the additional hoof shoed to 

 walk upon. We must therefore exclude, on the 

 instance of this last feature in this reversion, the 

 statement of Owen, that the splint bones of Hipparion 

 must have " dangled by the side of the large and 

 functional hoof (or third toe) like the pair of spurious 

 hoofs behind those forming the cloven foot in the 

 ox." Hensel's observations show that this inner 

 digit was the last to become suppressed when the 

 manus assumed the condition found in the Equus of 

 to-day, a matter we should have been inclined to 

 suspect, not knowing this, on the grounds of 

 atavistic reasoning. I would also quote Riitmeyer's 

 " Researches on the Dentition of the Horse," as a 

 case too in point. He has shown that the definite 

 dentition of the precursory genus is repeated in 

 the milk dentition of the succeeding genus, and 

 "Phylogenesis is unequivocally expressed in Onto- 

 genesis" (" Beitrage zur Kenntnis der fossilen Pferde," 

 Verhandlung der Naturforschenden Gesellschaft in 

 Basel, 1863). 



(To be continued.) 



EOZOON CANADENSE, THE PSEUDO- 

 DAWN OF LIFE. 



By J. Walter Gregory. 



[Continued from /. 86.] 



THERE were one or two objections which 

 seriously jarred with this interpretation. Fo- 

 raminifera are generally microscopic in size, and at 

 most but a few inches in diameter : hence the dis- 

 covery of one covering acres, was matter for surprise, 



though to be sure it is American. The idea also of 

 an animal living and prospering in a sea but a trifle 

 below boiling-point, suggested a few grave suspicions, 

 though one might be unable seriously to discredit it. 



Let us now turn to an examination of the evidence 

 on which the organic nature of Eozoon has been 

 assailed, and then of that settling its true minera- 

 logical position. 



We have seen that its supporters claim that all the 

 essential structures in highly organised foraminifera 

 are here represented, so it will be best to go through 

 them seriatim, to compare them more closely with 

 foraminiferal types, in order not to be misled by 

 superficial similarities ; and, perhaps before doing so, 

 to utter a word of warning against the figures usually 

 given in text-books as diagrammatic, representing 

 things not so much as they are but as interpretation 

 reads into them. 



First in order come the supposed casts of the 

 sarcode chambers, "serpentin korper" (serpentine 

 bodies) as Moebius calls them ; he objects to their 

 organic origin on account of their excessive varia- 

 bility in size, and dissimilarity from such chambers 

 in form and arrangement ; in foraminifera these 

 are on one fundamental plan, such as a ball or 

 lentil, crescent or sickle, " which in all the chambers 

 of a foraminiferal species point back to one and 

 the same law of formation," as he says in his 

 Memoir,* but in Eozoon the only observable regu- 

 larity is when the contours are similar to those of 

 olivine crystals ; this suggestion as to their origin is 

 in agreement with that advanced by King and 

 Rowney, who regard them as mere granules of 

 serpentine, a mineral mostly due to the alteration of 

 olivine or olivine-bearing rocks, and their occurrence 

 in a matrix of calcite as analogous to the crystalloids 

 of parasite in calcite, or those of coccolite, diopside, 

 &c, in Tyree marble. 



The case against the proper wall is far more 

 conclusive. In the first place, the researches of both 

 King and Rowney and of Moebius make it clear 

 that it is not truly analogous to the proper wall of 

 foraminifera, as this fibrous layer is supposed to be" 

 a series of casts of the pseudopodial tubuli through 

 the chamber walls ; but in many specimens the 

 fibres are placed in actual juxtaposition (as in Fig. 48), 

 whereas in foraminifera they are always isolated 

 tubes scattered through the body wall. Their shape 

 as well as their arrangement militates no less de- 

 cisively against their foraminiferal nature ; -in fora- 

 minifera they are cylindrical tubes, but in Eozoon are 

 prismatic needles or plates. In foraminifera, without 

 exception, they go to the surface by the shortest pos- 

 sible route, and only curve or emerge at an angle when 

 by so doing they can shorten their length ; in Eozoon 

 no such arrangement occurs ; they branch off tan- 



* " Der Bau des Eozoon Canadense nach eigenen Unter- 

 suchungen vergleichen mit der Bau der Foraminifera," " Palae- 

 ontographica," vol. xxv. 



