MEMORANDA 239 



fine point, and wlach, together, are very nearlj the shape of 

 a semicircle. 



Tfiese simple points (a, fig. 1) and forks (b) alternate along 

 both sides of the line of division, the forked extremity of one 

 divided spiral being placed in juxtaposition with the simple 

 point of the adjacent fibre. It is evident that the portion 

 which I have endeavoured to draw, although showing this 

 structure very clearly, is rather distorted in the process of 

 mounting (mounted by Topping) ; but from what may be 

 seen in other portions of this specimen, I believe that a tube 

 quite undistorted would present something of the appearance 

 of figure 2. This very beautiful structure is obscurely indi- 

 cated in the positive photograph by Mr. Delves, alluded to 

 above. By carefully examining the proboscis with a power 

 of about 200 diameters, it appears as though these tubes are 

 connected together by a delicate, structureless membrane, not 

 071 the same plane, with the membrane accurately represented 

 in figure 29 a, Plate 26, of the ' Micrographic Dictionary ;' in 

 wdiich figure, however, the peculiar features of the " divided 

 absorbent tube " do not appear (with all due deference to the 

 talented Authors) to be characteristically drawn. — G. Hunt, 

 Handsivorth, near Birmingham, 



Apciturc of Objcct-Giasses. — Professor Bailey having admitted 

 that the effect of balsam mounting is to cause a reduction of 

 the angle of aperture of the object-glass, any further remarks 

 from me in defence of this position are almost superfluous. 



A scientific controversy should not, perhaps, be avoided, if 

 its sole end is to establish the truth — my arguments on the 

 subject in question have been entirely dictated by this motive. 

 If I have at all misunderstood Professor Bailey, it has not 

 been either intentionally or wilfully, for the few words to 

 which his last comments relate might readily bear the inter- 

 pretation that I put upon them. He stated that my argu- 

 ments were erroneous, and gave as the single reason that I 

 had " traced the rays into the balsam instead of out of it ; " I 

 must confess that I inferred from this that Professor Bailey 

 meant to imply that a ray traced outwards would be refracted 

 at a different angle of emergence relative to the degree of 

 incidence, than if the same ray was traced inwards. As this 

 can never be the case, and the discussion related to one point 

 only, viz., the aperture of the object-glass, or angle of rays 

 collected from an object in balsam, therefore, with all submis- 

 sion, I think that 1 was not in fault in saying that it comes to 

 precisely the same thing if the rays are traced into the re- 

 fractive medium or out of it, as far as the actual result is 

 concerned. 



