434 CETACEA. 



jaw, but its edges are free to a little way behind the angle of the mouth, and thus must 

 have considerable mobility. In young specimens, 54 inches long, it is traversed by 

 a raphe which is nearly co-extensive with the free margins, but directed from the 

 mesial line at the tip to the right side. There is no trace of a foramen caecum or 

 of circumvallate papillae ; the tongue being remarkably smooth, only a few minute 

 fungiform papillse occurring on its sides, some distance beyond the angle of the 

 mouth. In its free portion it is thickly clad with filiform papillae. Below the free 

 margin, immediately behind the tij), there are small glands which open by four 

 orifices, generally arranged in a linear series with an azygos orifice above them. 

 Behind the posterior half of the free border of the tongue and below it, there is a 

 longitudinal row of large patulous orifices, generally tln-ee in number, with two or 

 three more forming an arch above them. They increase in size from before back- 

 wards, the most posterior being divided by a vertical pillar into two openings. The 

 orifices lead into sacs or recesses in the mucous membrane, into which one or more 

 glands appear to open. In close connection with them, and above and behind them 

 on the side of the free border of the tongue, there occurs a large patch of glandular 

 orifices of various sizes, some of the more anterior openings being more or less 

 surrounded by free folds of the mucous membrane, so that the surface appears rough 

 and the orifices to be protected by valves. These orifices do not occur further back 

 than the free margia, and are restricted always to the same spot. The lingual 

 racemose glands are especially numerous on the root and sides of the tongue, and 

 each gland appears to open by a distinct orifice, but the glands are not so long as in 

 Orcella, although they have the same structure. In the adult, the root of the tongue 

 is frequently corrugated, the corrugations simulating circumvallate papillae, but in 

 the young, as already stated, it is quite smooth. In the adult also the raphe cannot 

 be distinguished. 



Minute structure of its Fainllce. — The filiform papillae of the tongue micro- 

 scopically manifest two distinct characters, each having a special distribution. On 

 the front they are generally much more numerous than on the back part of the 

 tongue, and on the former they are fuUy three times as large as on the latter locality. 

 These anterior papillae are more or less conical in form, but some are much 

 broader and stouter than others, and their distinguishing feature is the division of 

 their summits, and occasionally of their sides, into short non-divergent processes. 

 These are very minute, and require a high power to demonstrate them satisfactorily. 

 Some of them are almost vesicular, and others are oblong and pointed at their free 

 ends, but aU are short and very obscure. The papillae clothing the back part of the 

 tongue, or that portion on which the majority of the mucous glands open, are very 

 minute flagilHform processes, situated generally on conical bases, while some are 

 essentially whip-hke, without any basal enlargement. 



Racemose mucotis glands. — Some of the orifices of those on the dorsum of the 

 tongue have a pyriform body visible to the naked eye, projecting outwards from 

 one side of the external termination of the duct. The base of this body is directed 

 outwards, and its apex is prolonged downwards into the duct for a short way as a 



