6.'.4 



HKPTILK-FUND 



KKPTILKS 



Hole source of transmissible variations in many- 

 celled animals. 



In the individual life tin- antithesis 1-ctween the 

 reproductive ami the nutritive functions has many 

 expressions, an<l in terms of this antithesis not a 

 few line* of variations can be rationalised. Thus, 

 the shortening of the axis of the llower seems to_be 

 the result of a check imposed upon the vegetative 

 system by the reproduction function; thus, the 

 development of gymnooperm into Mgkwpenn 

 suggests a continuous subordination of the repro- 

 ductive cnr]iellary leaf: thus, in almost every 

 natural alliance of phanerogams nniy be reo<l a 

 contrast lietween more ami less vegetative ty|K-s, 

 such as is seen within the limits of a single species 

 in the transitions lietween the leafy kale and 

 the cauliflower. Among animals the antithesis 

 is expressed in different ways OH in the varied 

 degree in which the reproductive individuals of 

 a hvdroid colony are differentiated from the 

 nutritive members. 



In considering the evolution of animals great 

 ini|M>rtance is always and rightly attached to 

 the self -preserving struggles and endeavours which 

 secure the satisfaction of nutritive needs ; but the 

 speeie-s.niainta.imng activities of reproduction have 

 been not less important. Thus, Darwin insisted on 

 the importance of sexual selection as a factor in 

 evolution, and, though the criticisms of Wallace and 

 others have lessened the cogency of Darwin's argu- 

 ment, there can be little doubt that courtship has 

 aided in the evolution of the psychical life of 

 animals. Romanes, too, in his insistence on the 

 importance of isolation, recognises 'the reprodno- 

 tive factor in evolution.' For by variations in the 

 reproductive system a species may In- divided into 

 mutually sterile sets, which, prevented from inter- 

 cr.ising by this physiological barrier, are free to 

 develop along divergent paths. In a very different 

 ronnec-ticni, Robert Chambers emphasised the ini- 

 ]Mirtanee of ' prolonged gestation,' and Fiske has 

 directed attention to the progressive intliience of 

 prolonged infancy, while' Miss liuckley has well 

 pointed out that an increase of parental care and 

 sacrifice as seen in birds and mammals has surely 

 been a factor in, as well as a result of, the general 

 ascent of animals. 



The increase of reproductive sacrifice which we 

 observe in the evolution of mammals and in the 

 progress through oviparous monotremes, prenm- 

 turely-liearing marsupials, and various grades of 

 placeutals : the growth of parental care, and the 

 frequent suliordination of self-preserving to cp> 

 maintaining ends ; and finally, the rise of sociality 

 from foundations based in organic kinship, are 

 well known facts of animal life which suggest the 

 ini|Mirtance of the reproductive factor in evolution. 



See KMBRYOUJOT, HEREDITY, SEX ; H. Spencer, 

 Principle* of Biologi (Lend. 1H04 >); K. Haeckcl. 

 relit SforpHotoffit (Berlin, 1866); V. llcnscn, 

 Pky$inlogu der Zmj>fi, in llcnnuin'* Hamlburh <lrr 

 Phyiiolo-jie (Leip. 1881); mrticle 'Reproduction,' by P. 

 Oflddm nd H. H. Vines, in Kney. Bnt. ; A. Weimunn, 

 Papert on Heredity, lie. (Oxford, 18K9) ; P. Gedde* and 

 J. A. Thoiiuon, Ktolution of Sex ( Load. 1889). 



l!c |il ili'-Fiiml. the fund so calle<l, descrilx*d 

 at HASIIVKII, Vol. V. p. 547, was almlished by 

 Caprivi in IH90. 



Kr|itili*s. a very large clans of Vertebrate 

 animals, including Tortoises and Turtles, Lizards 

 of many kinds, the divergent New /calami 'lizard' 

 Sphciiodoii, Snakes, and Crocodilian* - live distinct 

 orders with living rcpicscntatives, but including 

 also at least as many orders of wholly extinct t\ JM-. 

 such as Ichthyosaurs, I'lesiosaurs, and Deino- 

 anrs. 



Reptiles occupy a central position in the Verte- 

 brate erie : beneath them are Amphibians and 



Fishes, above them are Itirds and Mammals. They 

 begin the series of ' higher Vertebrates,' \\hich at 

 no |>ciiod of life breathe b\ gills, which in cinhiyunic 

 life are provided with two birth robes or fect.cl 



mliranes a |uotcetivc amnion and a respiratory 



allantois. Their relationships seem to be three- 

 fold, with tin- Amphibians, with Itirds, and with 

 Mamma!-. Hut there is no doubt that they arc 

 most closely linked to Itirds a fact lirst cleaily 

 recognised by Huxley, who emphasised the deep 

 structural affinities of Itirds anil Reptiles by link 

 ing them together as Sauropsida, in contrast to 

 Mammalia on the one hand and Ichthyopsidn 

 (Amphibians and Fishes) on the other. 



Referrinir to the article l!li:i>s for a contrast 

 lietween Mammal*, Mirds, and Reptiles, we shall 

 simply notice that Reptiles are cold-blooded, tin 1 

 temperature of the l>dv not greatly exceeding that 

 of the surrounding medium; that the heart is tl 

 rhiunliered, except in Crocodilians, where four 

 chambers first occur; that mostly venous blood 

 goes from the heart to the anterior viscera, and 

 mixed blood to the posterior region, only the head 

 and anterior regions receiving purely arterial blood ; 

 that the body is covered with scales, with which 

 subjacent bony plates or scutes are some! 

 .Associated ; that (he skull articulates by a MI 

 conch le with the backbone, and the lower jaw 

 Worn against the quadrate bone ; that the great 

 majority are oviparous, while in some the eggs 

 are hatched within the mother. The earliest 

 remains of Reptiles are found in Permian strata, 

 and the golden age of Reptiles was in Mesozoic, 

 (specially in Jurassic and Cretaceous, times. 



I'/tix.iirii'ii/inii (</' l.iriiii/ li'i-fitilet. As the orders 

 of Reptiles with living representatives are separately 

 discussed, il will IK* enough here to give a general 

 classification. Order 1, Chelonia : Tortoises and 

 Turtles. 2, Rhynchocephalia : one fonn the New 

 Zealand lizard Sphenodon (q.v. ), whose extinct 

 ancestors date from the Permian. 3, Lacertilia : 

 Lizards (q.v.). 4, Ophidia : Snakes (q.v.). 5, 

 I'rocodilia : Crocodiles (q.v.), Alligators (q.v.). 



EXTINCT RKPTII.KS.- The classification of tjie 

 extinct Reptilian type's is still very uncertain; 

 but many authorities agree in recognising the 

 following orders : 



AnuiiKiilniiliii.- Reptiles with lizard-like l*ody, 

 limbs adapted for walking, biconcave veitebne, 

 and teeth lixecl in socket*. The order is restricted 

 to the Permian and Trias, and exhibits afliniticH 

 with the Labvrinthodont Amphibians and with 

 Mammals. Among the representative genera are 

 Pariasaums, (Jalesaurus, Ueuterosauriis, l>ic\ 

 nodon, and Placodns. 



Savrujitrrityiii.- Reptiles without exoski'leton, 

 vith long neck and short tail, limbs adapted for 

 walking or for swimming, biconcave verlchric, teeth 

 fixed in sockets. All of them seem to have been 

 carnivorous. The order is represented from tin- 

 Trias to the I'ppcr Chalk, and exhibits aflinities 

 with Amphibians. Among the representative 

 jencra arc- I'lesiosaurus, Mesosaums, and Notho- 

 Haiirus. 



Irlitlin/itrriiijia. Marine Reptiles, with whale- 

 like IMM|V, wit lie. ut exoskelelon, with limbs modilic'd 

 as paddles, with biconcave vertebra 1 , with teeth 

 implanted in a continuous groove. Many were 

 carnivorous and fed on fishes. Scelcy has shown 

 that some were viviparous, the fossilised young 

 1-eing found in the fossilised mothers. The order 

 is represented from the I'ppcr Trias to the I ppcr 

 Chalk, and exhibits allinit ies with Lab\ Tintlioelon! 

 Amphibians and with the' New Xcahind 'lizard'' 

 Bpbenodoa. Among the genera are Ichthyosaurus 



and Optlmlmosaurus. Some' attai 1 a length of 



30 to 40 feet. 



JiJiyncocephalia. As Sphenodon is the only 



