6 PROF. W. N. PARKER ON THE [Jan. 16, 



An examination of the end of the snout with a hand-lens shows 

 the presence of a number of fine dots on both jaws extending 

 about as far back as the gape. These are indicated in figs. 1 and 2. 

 Sections show them to be due to the presence of funnel-shaped 

 apertures in the horny layer, which extend inwards, surrounded 

 by a continuation of the horn, and gradually become narrower 

 (figs. 4, 5, 12, and 13). Just beneath each aperture the epidermis is 

 prolonged inwards to form an elongated oval process (fig. 12), which, 

 slightly below the base of the dermal papilla?, narrows somewhat 

 to form a tube extending for some distance into the derma, where 

 it becomes convoluted ; its walls are composed of a double layer 

 of cells, and the lumen becomes greatly coiled on passing into the 

 swollen base of the epidermal process and then communicates 

 with the aperture at the base of the horny ingrowth. It will thus 

 be seen that these glands are precisely similar in structure to 

 ordinary sweat-glands. I should mention that the lumen is not 

 developed in the young stages. 



Poulton l has described structures in Omithorhynchus which are 

 apparently similar to these, and suggests that they may correspond 

 to modified hairs ; this, however, seems tome improbable. I have 

 found nothing which could correspond to the sensory organs of the 

 bill of Omithorhynchus described by Poulton. 



No hairs, nor any structures resembling hairs, are present on the 

 horny snout. Behind this, hairs are developed in abundance (figs. 

 2 and 10), and in the older stage the sebaceous glands can be seen 

 arising as buds from the hair-follicles. No sweat-glands are 

 present on the hairy part of the head ; the rest of the body I 

 have not yet examined. It should, however, be remembered that 

 G-egenbaur 2 has shown that the mammary glands are modified 

 sweat-glands in these animals. 



III. The Oral Cavity. 



Even in the younger stage the mouth has already acquired its 

 narrow and tubular form (see figs. 5-7, 10, and 14). The elongated 

 tongue is covered with a thin layer of horn at the tip. The sub- 

 lingual glands are numerous, and open at various points into the 

 floor of the mouth. The naso-palatine canals communicate with the 

 oral cavity anteriorly (fig. 6, vp.c.) ; and from this point backwards, 

 some distance beyond Jacobson's organ, a number of simple gland- 

 tubes, very similar to those already described in the snout, are 

 present on the roof of the mouth (tig. 7). Similar glands are also 

 present in this region in the young Omithorhynchus. 



The epithelium in certain regions both above and below gives 

 rise to horny teeth, which on the anterior part of the lower jaw 

 form marked ridges (figs. 5, 7, 14, 16). A dermal papilla extends 

 into the thickened epithelial ridge, which produces a thick horny 

 layer on its outer surface. 



1 " On the tactile terminal Organs and other Structures in the Bill of Omitho- 

 rhynchus," Journ. Pbysiol. vol. v. p. xv. (Proc. Physiol. Soc. 1884). 



2 ' Zur Kenntniss der Mammarorgnne der Monotremen,' Leipzig:. 1S8R. 



