18 C'O.MPAKATIYK ANATOMY. 



a~ well ae similar element = c..nnecte<l with ./.implicated pieces of apparatu.- 

 will be tivale.1 .if later in c..imectioii with the sense orpins. 



The ineaniii'.' cf tin- "granular cells" present in the intern im-i it of 

 Petrmny/iin. a.- well as of the so-called "club-" and "goblet-cells" in the 



nianv-hiveiv.l epidermis of osseous Fishes, i- as yet by no mean- dear; it 

 is, however, not improbable that the latter of the.se have to ilo with the pre- 

 paration .if a secretion which protects the outer skin from the action of 

 the water. 



The scales of Fishes lie in connective-tissue pouches of the 

 derma, and are formed as ossifications of the latter. In Teleostei 

 they are covered by the epidermis throughout life ; in Ganoids and 

 Elasmobranchs this is only the case in the larva. (For further 

 details compare pp. 31 and 32.) 



Pigment-cells (cp. p. 16), which are under the influence of 

 the nervous system and are able to cause a change of colour, are 

 present sometimes in both layers of the integument, sometimes in 

 the epidermis only. Muscles and glands, such as are found 

 in the skin of other Vertebrates, are not usually present 

 in Fishes. 1 



Phosphorescent organs are present in the internment of some Fishes. 



Amphibia. The structure of the integument in larval Am- 

 phibians somewhat resembles that of Fishes, while in adults it 

 more nearly approaches that seen in Reptiles. 



The epidermis of those larva? which live in the water consists 

 of two sharply differentiated layers. The outer layer is made up 

 of flat cells with a striated border (Fig. HA, CV?) on their free edge, 

 like that already described in Fishes: the inner layer is composed 

 of more cylindrical or cubical cells (&). The former corresponds to 

 the stratum corneum, the latter to the stratum Malpighii. 



Later, with advancing development, the layers of the epidermis 

 become more numerous, and involutions towards the derma take 

 place in all parts, giving rise to a great number of globular and 

 tube-shaped glands, which are particularly abundant in certain 

 regions more especially in the head and flanks. 



Their secretion serves to keep the skin moist, but, as experi- 

 ments have shown, it tdso 1'urms an important weapon of defence, 

 on account of its poisonous properties. 2 



1 Then- .-ire. In. \\.-v.T, several except i.. us In tliis nihi. In male Klasin.ibniiichs 



t lleiv i.-, a lae_re 1,'Un illl I a pt e rv 1,'opiid ' ' .^' ; i]id "'' t'l' 1 cla.-pclj at tile Kase ut'eaeli 

 pelvic lill. It 811868 as a tlllic-like ill Va - ilia t i. HI of the skill, ail'l is ill relation with 

 the enplllatnl V ( H ^a 11 - I e] i. tile chapter nil these ol-alls . In (he WceVtT i Tl a ell i 1 1 US I 

 (here is a series of piiisnn-elalids IvillJ,' nil either si.le of the liases of (he spines .it' the 



ilnr.-al tin: they :nv sitiiatc.l at the li.iltoiii f integumentary sacs, and llieir iliicts 



Open clo-e tn the lia-es of the spines. Ill Thalass.>phr\ IM- tile (iperellllllll is ]in>- 



vi'lcd \\ith a hnlliiw spine, a I (lie has,- .if which a poison-sac is sitnateil, and in 



Syirilieeia there are also a s.-ijes of " pnisnn-liau's " at the hases .if tli. uTuoVed 



nines H iniith. r . \'\ ..... ..i-'ans appear to lie present in certain ..( h. r Fi-hes 



(many Si hi n. ids, ,\,-tnl,atis| hut the exist, m . ..(' act ual glands is not certainly known. 

 'flu- ]...i-i,ii has I,,, , .(]',., t mi . .1 her individuals ol i he same spei i.-s ; hut it aeta 

 Verj jioweifnlly mi ch.sely allied I'm ins. as \\ell as on the higher animals. 



