33 



be soaked it is impossible to say — it depended upon temperature and otber cir- 

 cumstances, and it might be perhaps from five minutes to as many hours, no 

 one could tell beforehand how long a time would be required. The glands 

 must be taken from the insect and put immediately into the solution, which 

 must be kept in the dark ; when sufficiently soaked they must be well washed in 

 distilled water, and after that they should be put into more distilled water and 

 exposed to strong daylight until they acquired a beautiful purple colour. If 

 such a preparation were then examined with a high power — nothing less than a 

 good £ would be of any use— there would be seen a fine network of nerves 

 (diagram drawn on the black board representing what would be seen if the 

 observer were lucky). He considered that it was extremely probable that all 

 the nerves of special sense end in modified epithelial cells. In the ear it is well 

 known that there are great numbers of hairs — four or five thousand of them — 

 all tuned to receive and transmit different sounds to the nerves with which they 

 are connected, and which nerves all end in epithelial cells. In the nose and 

 in the tongue the same kind of thing occurs, and in the eye there are found 

 what might be regarded as a modified epithelial structure in the rods and cones 

 of the retina. Now when they had all this evidence of the termination of 

 nerves in cells, the one seemed to substantiate the other, whereas if they had no 

 instances of the kind to refer to there might perhaps have been room for doubt 

 with regard to Pliiger's statements ; when they thought of the extreme delicacy 

 of the investigation, and that the few persons who had followed it out had con- 

 firmed Pliiger's view, he thought there was very good ground indeed for believ- 

 ing it to be the correct one. He thought that if Mr. White would try the 

 process he had suggested (and he knew that he liked working in gold), he would 

 no doubt be able to demonstrate the fact. He might say that he had never 

 seen better specimens of the glands than those which were exhibited by Mr. 

 White and Mr. Tatem. Eeferring to the portions coloured red in Mr. White's 

 diagram, Mr. Lowne explained that these were certainly absent in the fly, which 

 possessed what was known as the tubular form of salivary gland, one which was 

 common to all suctorial insects. The beetles and gnawing insects have another 

 form of gland ; and in the cockroach and the hemiptera two pairs of glands are 

 found. In the human subject there were three kinds of salivary glands, one of 

 which supplies a quantity of viscid saliva, another produces large quantities of a 

 more watery kind, and the 3rd, or sublingual glands, furnish a small quantity 

 of very viscid saliva — and as it was quite clear that in vertebrates there are 

 three kinds of saliva, he thought there was nothing improbable in the idea that 

 there migtft be two kinds of saliva in insects. The ringing of the tubes was no 

 proof whatever that they are tracheal tubes, because all, or nearly all, the 

 tubular structures in insects exhibit rings. He had never seen the air sac 

 of any insect collapsed after death — they were all made of elastic material — the 

 insect had the power of compressing them, but they were naturally kept open 

 by their own elasticity. In our own cases the air is forced out of the lungs by 

 their elasticity, but in insects the opposite condition occurs. When the insect 

 is dead these sacs are said to be always found empty, and no one has ever 

 found them either before or after the death of the insect filled with air. He 

 asked where is the evidence that they are air sacs ? And when they had 

 before them such very conclusive evidence that they are not, he should 

 certainly continue so to regard them until very convincing proof to the contrary 

 is produced. 



The President, after announcing that the Club was that evening honoured by 



D 



