Kasdl Passiif/es of the Cachalot. (M3 



left blow-holes respectively. One of these, the rij^ht, con- 

 tiiiues to be coiiiieoted with tlie comiiiou chiiinlier, as we 

 fnay teim it; but as it passes backwards, ?'. 6'., along tlie 

 loni;itutliiial axis of the body — and therefore at riglit angles 

 to the anterior orifice of the chanihei", — it opens along the 

 side of that ehaml)er. On the other hand, the orifice of the 

 left nasal tube has a diflerent course as we trace it backwards 

 from its opening into the conjoint anterior furrow. It 

 becomes freed at once from its connection with the anterior 

 furrow, and is seen in the transverse sections as a perfectly 

 independent groove. 



I have directed attention in my earlier communication on 

 this foetus, in the paper referred to below "^^ to the fact that 

 tlie left blow-hole is longer than the right — or, rather, than 

 that part of the right blow-hole which is distinctly lateral 

 in position ; for it is impossible, as I have just shown, to 

 draw an absolute line of demarcation as to where the lateral 

 region is to be distinguished from the anteiior furrow. 

 This is not quite so clear in the figures which I then gave 

 as it might have been ; this, however, is due to the curvature 

 of the sides of the head and the consequent view of the 

 furrow partly in profile. I have been able in my micro- 

 scopical examination of the foetus to compare the lengths 

 more accurately by counting the actu.al sections, and 

 comparing the numbers which contain, with those that do 

 not contain, the grooves of the two blow-holes. I have found 

 that the right blow-hole runs back through 20 sections, 

 while the left is prolonged backwards for another 44 sections, 

 being thus about three times its length. The actual 

 measurements work out at 1'6 mm. in the ease of the left 

 furrow and '5 mm. in the case of the right-hand one. The 

 disparity, however, must be rectified by the extension round 

 the corner — so to speak — of the right blow-hole. But, in 

 any case, the left blow-hole furrow does reach further back 

 than its fellow of the right side. The asymmetry of the 

 head is already well established in this foetus, as will be 

 pointed out in the case of other structures as well as the 

 blow-holes. 



§ The Course of the Two Nasal Passages to the Point where 

 they unite to form the Nasal Pharynx. 



It will have been gathered from the foregoing account of 



* Loc, cit. Auu. Duibun Mas. 



42- 



