654 On Blow-holes and Nasal Passages of the Cachalot, 



that the tonsils are asymmetrical. For the left gland not 

 only appears first but ends last. 



There is a further asymmetry between the two tonsils. 

 It is only that of the left side which possesses a coasting of 

 lymphoid tissue upon the canal of the tonsil. This seems 

 to be completely absent in the case of the tonsil of the right 

 side. The canal is quite dorsal in position, and runs upwards 

 for its greater length, and then bends quite — or nearly so — 

 at right angles to run backwards for a little way. In the 

 series of transverse sections, therefore, the canal is for the 

 greater part of its extent cut longitudinally, and then the 

 extreme distal end is cut at right angles. The opening 

 into the oropharynx is really rather slit-like, only the 

 median part of this slit being prolonged into the tube. The 

 particular form which the tonsils of this animal show are 

 interesting in view of the general state of affairs as to the 

 tonsils in the Mammalia — a subject which has lately been 

 reviewed with many additions. 



In the paper referred to * the authors regard a long 

 tubular tonsil as " the starting-point of the series,^' and this 

 condition, occurring in the tiger and the leopard, is to be 

 seen in the early foetal condition of man. It is to this type 

 that the tonsils are to be referred in the Sperm- Whale, as it 

 appears to me. But the conditions are much exaggerated 

 in the whale. Its independence of the walls of the pharynx, 

 and the length to which it projects outside of those walls 

 in a foetus, which, though small, is in some respects very 

 advanced, are highly remarkable. This is so obvious that 

 it need not further be commented upon. 



The comparison of this tonsil with a rudimentary^ gill- 

 cleft is also obvious. But the position might at first appear 

 to militate against this generally-accepted view. In the 

 case of the Eustachian tube, the origin of the tube is dis- 

 tinctly ventral, but the tonsil is as distinctly a dorsal 

 outgrowth of the lining epithelium of the oropharynx. 

 There is, as I think, no possibility of denying their essential 

 similarity. If it be held that the posterior part of the 

 nasal passage or passages is not a part of the primitive 

 ingrowth of the olfactory organ, but a longitudinal division 

 of one tube, then the differing position of two, probably 

 serially homologous, outgrowths becomes intelligible. For 

 if we, so to speak, rejoin the two tubes oral and respiratory, 

 the two pairs of diverticula will both be relegated to, and 



* Seccombe Hett and Butterfield, " The Auatoni}' of the Palatine 

 Tonsils," Jo urn. Auat. Phys. xliv. p. 35. 



