856 RECORD OF CURRENT RESEARCHES RELATING TO 



and he congratulates liimself on having shown the direct descent of the 

 nucleus of segmentation from the germinal spot. Although the ger- 

 minal vesicle disappears the sjiot gives rise directly to two new 

 nucleoli ; and the theory of Haeckel, which requires the presence of, at 

 some stage, a cytod, or non-nucleated cell (ovum), must be conse- 

 quently modified. Earlier observers have, however, stated that the 

 ovum is always nucleated ; and it is to be hoped therefore that some 

 observer will, as M. Perez suggests, submit his observations to an 

 " infallible criterion " — the examination of ova which are developed 

 parthenogenetically. 



Cutaneous Absorption of Helix pomatia.*— M. Mcr has made 

 some experiments on the curious faculty possessed by the snail of 

 absorbing a large quantity of water; first noted by Spallanzani, it 

 was cited by the eminent physicist Dutrochet as a remarkable example 

 of the power of osmotic forces. 



1. A Helix pomatia, entirely immersed in water, absorbed it not 

 only by its integument, but also by the walls of its pulmonary sac and 

 of its digestive tube. If a healthy example is nuder observation, the 

 experiment may be continued for three days, but the quantity absorbed, 

 though exceeding in weight the snail itself, is not taken in regularly ; 

 absorption, very rapid at first, continually decreases, though without 

 altogether ceasing, until the moment of death. 



2. So too with regard to the expulsion of the absorbed water ; 

 when the animal is removed to air, the water is at first got rid of with 

 great rapidity, and the excretion becomes gradually less. 



3. The period of excretion is longer than that of absorption, but 

 even then all that has been absorbed is not excreted, owing to the fact 

 that, previous to the experiment, the tissues of the animal did not 

 contain all the water which they were capable of holding. 



4. In correlation with this it is to be observed that if a snail 

 is removed from the water after a period of immersion lasting only 

 for two or three hours, it takes a considerable time to rid itself of the 

 fluid which it has so rapidly absorbed. 



5. The amount of water absorbed depends on the state of con- 

 traction of the muscles around the blood sinuses. 



6. If left in water after death, the tissues free themselves from the 

 liquid. 



7. The penetration of water ai:)pcars to have no effect on the con- 

 stituent elements of the body, and death appears to be due to the 

 resistance offered by the water to the active circulation of the blood. 



8. Although all parts of the body are able to absorb water, the 

 walls of the jjulmonary sac ajjjjcar to be most capable. 



Treated with such colouring agents as carmine, aniline blue, or 

 rosaniline, the snail exhibits, with weak solutions, no other phenomena 

 than those observed with water ; but it is to be observed that the 

 colouring matters did not, in any appreciable quantity at any rate, 

 pass into the blood. Experiments with stronger solutions are de- 

 scribed in detail, and the author comes finally to the consideration 

 of the question, Is the penetration of fluids effected by passages 

 * ' CR. Soc. Biol.' for 1877 (1870), p. 186. 



