738 REPORT — 1887. 



external nasal tube persisted, although in modified form. The olfactory nerve, 

 gradually decreasing in size, became at the same time pushed outwards until it 

 reached the level of the skin. 



Thus the condition of things seen in Tetrodon pai-dalis and Diodon maculatus 

 VFas reached. The Schneiderian folds formerly present in the olfactory sac were 

 then replaced by the above-described processes on the inner wall of the nasal 

 folds. 



The hollow olfactory tube may be considered as a protective arrangement for 

 the nerve end-organs, but its structure became changed in the course of phylo- 

 genesis. As the two apertures in its wall gradually became elongated, so as to 

 reach to the distal end, they eventually caused a splitting of the nasal process into 

 two solid limbs. 



This stage is represented by Tetrodon nigropunctahis, immaculatus, and hispidus, 

 while a still further regressive development of the organ has taken place in 

 Tetrodon papua, in which the last stage of the whole process is reached. 



It is not impossible that species of Tetrodonts exist in which a still further 

 degeneration has taken place, so as to cause an entire disappearance of the olfactory 

 nerve. 



These facts seem to me to have a still further interest inasmuch as they show 

 that the olfactory organ, as well as the eye of vertebrates (compare Gi/mnophiona, 

 Proteus, Amblyopsis, &c.), may pass into an unstable condition, should it become 

 necessary in the interest of the animal as a whole. 



Further histological researches must show whether this peculiarly modified 

 nasal organ in Tetrodonts is still physiologically an olfactory organ, or whether it 

 lias undergone a change of function. 



5. On the Torpid State o/ Protopterus. Hy Professor Wiedeesheim.^ 



In July last I received some living specimens of Protopterus, from the river 

 Gambia, which had been taken during the torpid period and sent to this country, 

 still enclosed within clods of earth. One of them had been set free on the previous 

 day, while two clods were still intact. 



In both of the latter, as previously described by Mr. Bartlett, a round aperture 

 could be seen, leading into a smooth-walled tube aliout 15 centimetres in length. 

 Only one of the clods, however, was found to contain a specimen ; from the other 

 the animal had already escaped. 



In opening up the clod I intentionally followed a different method from that of 

 ray predecessors, all of whom without exception set free the animal by softening 

 the earth in water. 



Although this is undoubtedly the most delicate method of operation, it renders 

 it impossible to see the animal undisturbed in its natural position within the 

 enclosing capsule or so-called cocoon. 



I therefore carefully broke away the earth, bit by bit, with a hammer and 

 chisel till the dark-brown capside was exposed. This latter was of a tolerably 

 regular oval form except in that region where the tube abutted against it. In this 

 place it was flattened and oblique in position, reminding one of the human tym- 

 panic membrane. This does not correspond with Bartlett 's description, but my 

 observations closely agree with those of Krauss on this point. 



I cannot be certam whether this flattened portion of the capsule was perforated 

 by an aperture, as described by former observers ; but it seems to me to be in the 

 hio-hest degree probable that such an aperture was present, inasmuch as the snout 

 of^the animal was closely pressed into the acute angle formed between the flattened 

 membrane and the rest of the capsule wall. 



I have nothing to add to Erauss's description of the enclosing membrane, but 

 I hope shortly to be able to give an account of its chemical nature, which is being 

 determined by my friend Professor Baumann, of Freiburg. 



It may, however, be stated with certainty that the capsule consists of a 



■ Published in the Anatomhcher A7iznger. Jena, 1887. 



