106 PHYSIOLOGICAL SERIES. 



closely adherent to the skin of the back along the border 

 of the spine-bearing area, and a series of small muscles 

 arising from the head, fore limbs, tail and ventral mid-line 

 of the body, and inserted into the inner margin of the orbi- 

 cularis panniculi. These latter muscles draw the extremities 

 together and at the same time drag the orbicularis panniculi 

 so far towards the ventral surface that it can act like the 

 running string in the mouth of a bag and cause the complete 

 enclosure of the animal in the spine-bearing region of the 

 skin. Unrolling is caused by the action of the longitudinal 

 and transverse fibres of the dorsal region of the skin, with 

 the help of certain small muscles arising from the skull and 

 vertebral column, and so arranged that they draw the skin 

 towards the middle of the back. 0. C. 64 z n. 



C. 81. Head and fore limbs together with the anterior half of 

 the skin of a Hedgehog (Erinaceus europceus), showing 

 many of the cutaneous muscles in this region more clearly 

 than in the previous specimen. 0. C. 64 z o. 



C. 82. Hind limbs and posterior half of the skin of a Hedgehog 

 (Erinaceus europceus), showing the cutaneous muscles. 

 O.C.64z^. 



Himly, Ueber das Zusannnenkugeln des Igels, Bruns- 

 wick, 1801, p. 28. 

 Dobson, Monograph of Insectivora, 1882, p. 41. 



Head and Neck. 

 Huge, Festschr. Gegenbaur, Bd. iii. 1896, p. 195. 



C. 83. Left half of the head and branchial region of a Dog-fish 

 (Scyllium catuhis), from which the skin has been removed 

 to show the superficial muscles. These, with the exception 

 of the large adductor mandibulse, are all derivatives of a 

 common superficial circular layer (constrictor arcuum), 

 the main function of which is to expel the water from the 

 pharynx through the gill-openings. 



C. 84. Right half of the head and branchial region of the same 

 Dog-fish showing the deeper branchial muscles. These 



