663 



the layer of blubber." The reason for this is to be found in the 

 fact thai hair is but a poor defense against the loss of heat when 

 in the water, while the layer of oil constituting the blubber 

 affords an excellent protection. Accompanying the loss of the 

 hair we naturally find also a reduction in the sebaceous glands, 

 smooth muscles and nerves of the skin. The sweat glands are 

 also wanting in the Sirenia and Cetacea. 



There are indications that the toothed whales, Odontoceti, 

 have been derived from forms possessing a dermal armature. 

 Kiikenthal, to whom this observation is due has shown that in 

 Neomeris there remains in the adult considerable vestiges of 

 what must be looked upon as a dermal armor. This has been 

 preserved usually only in those regions of the body where it may 

 be useful as a protection, as on the anterior margin of the flip- 

 pers, the anterior dorsal region and around the blow-hole, though 

 traces may occur on other parts of the body. The study of the 

 embryo shows that this is only a remnant of what was once a 

 much more extensive dermal armor. In the porpoises is found 

 the last appearance of this armor in the tubercles along the 



It is worthy of note in this connection that there have been 



whales. The loss of armor is paralleled a number of times in 

 the marine reptiles. In the ichthyosaurs, the most aquatic 



