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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



If an arrangement exists fitted to prevent the 

 flowing away of the liquid contained in the com- 

 partment which holds the branchiae, the animal 

 will be able to live a pretty long time in the open 

 air. Eels, which are fond of rambling about, and 

 venture into the middle of meadows without dan- 

 ger, owe that power to the mode of closing up 

 their respiratory cavity. The anabas of Indian 

 rivers, the gourami of China, are very much bet- 

 ter furnished ; they have a true reservoir formed 

 of cells surrounded by leaf-like plates ; thus, with- 

 out the least inconvenience, they can leave their 

 usual abode, and even make tolerably long jour- 

 neys; the water from their reservoir flowing out 

 slowly moistens the branchiae. 



Like fishes, Crustacea in general live con- 

 stantly in the water. Some crabs, it is true, quit 

 the sea, but cautiously ; they do not go far from 

 the shore, and their excursions are not long. 

 Some species only penetrate into the land, and go 

 to a distance, ranging over the coun try for a month 

 at a time. These land-crabs, as they are called, 

 almost all prettily adorned with lively colors, are 

 spread through the warm regions of South Amer- 

 ica, and abound in the Antilles, where they mark 

 their passage through the fields with devastation. 

 They are distinguished from other crabs by a 

 rounded and very high shell. The advantage of 

 this arrangement is at once apparent : the shell 

 being very high, the respiratory chamber becomes 

 spacious ; and this chamber, well closed, lined with 

 a permeable membrane, being full of water, the 

 branchiae are constantly moist. The air breathed 

 is thus kept in a state quite sufficient for the 

 needs of respiration. For a crustaceous creature 

 which can climb trees, quite abundant on the In- 

 dian coasts, the Molucca and Seychelles Islands, 

 etc., the means of living a long time out of water 

 are provided by another arrangement, also very 

 simple. This creature, of large size, called the 

 robber-crab because it eats fruits, has neither a 

 very convex upper shell nor a very large respi- 

 ratory chamber; but above its branchiae is avas- 

 cular sort of vegetation, fit to retain moisture, 

 and acting in the manner of a sponge. Every- 

 where we succeed in establishing a close relation 

 between the organization and the aptitudes, be- 

 tween the instincts and the characteristics of ex- 

 ternal parts. It is thus that the conditions of life 

 imposed on each species seem to us determined 

 in a way that forces us to regard as impossible 

 any modifications that are at all considerable in 

 animated beings. 



There is one relation of a peculiar kind, most 

 interesting to follow in its different manifesta- 



tions — that which exists between the faculties of 

 adult animals and the condition of new-born ones. 

 The lower orders are of a constitution strong 

 enough from the time of their birth to supply 

 their own needs without aid from others. Those 

 species that offer us the spectacle of most admi- 

 rable instincts are born weak, and incapable of life 

 without the care of mothers or nurses. Among 

 the beings that suckle their young, do we not see 

 the most intelligent, the most gifted in all respects, 

 come into the world in a state of extreme weak- 

 ness, which imposes on parents and especially on 

 mothers the duty of watching over and protect- 

 ing their children for a long period ? Man is the 

 first and most striking instance of this. Among 

 birds there is a more marked difference than 

 among mammals, which all, without exception, 

 draw the first nourishment from their mothers. 

 Chicks, when they leave their shell, are even then 

 strong and able to get their own food ; they do 

 indeed follow their mother, and seem to seek her 

 protection ; but, if they stay close by her and 

 take refuge under her body, it is solely for the 

 sake of the warmth indispensable to all young 

 creatures. William Edwards, the famous physi- 

 ologist, showed nearly half a century ago that 

 in newly-born animals the power of producing 

 heat is seldom so much developed that the tem- 

 perature of the organism can be kept up to the 

 normal degree, if the atmosphere grows very 

 cold. The observations and experiments of nat- 

 uralists proved that young animals ought to be 

 kept very warm, and that in this respect the ma- 

 ternal instinct never errs. Tillerme and Milne- 

 Edwards ascertained, by a grouping of well-estab- 

 lished facts, that the human species is not ex- 

 cepted from the general law, and they were thus 

 led to protest against the barbarous regulation 

 which obliges new-born children to be carried to 

 the mayors' offices for registry, thus in fact expos- 

 ing them to the risk of death, if the cold affects 

 them. They demonstrated the danger with the 

 support of undeniable scientific facts, and yet a 

 few choice spirits needed unconquerable perse- 

 verance for forty years before they could over- 

 come administrative routine, and gain the aboli- 

 tion of a custom like that at Paris. 



If the young of the hen and the duck, birds 

 of very limited intelligence, have no other need 

 of the mother on quitting the shell than to warm 

 themselves by her, on the contrary, all those 

 charming birds that delight us by their songs, 

 their industry, their loves, their intelligence, the 

 more wonderful in our eyes the more daintily 

 small the creature is, all those that we train to 



