Boa-Constrictors of British Guiana. 303 



The above explanation may seem a fanciful one, but it is 

 hardly possible that, under the abundant opportunities for the 

 favourable attack on man by these water-boas under local 

 conditions, there should not be many cases known if man 

 were not naturally exempted. The fear of being seized by 

 these reptiles, which deters so many timid people from bathing 

 in the creeks and rivers, is no doubt natm-al enough, even if 

 such seizure may only happen by mistake ; but the chances 

 of danger are so infinitesimal, that they are hardly worth 

 regarding. 



Unlike the other boas, but like water-snakes and vipers 

 generally, the anaconda is ovo-viviparous. The eggs are 

 retained in the body until the young are fully developed and 

 able to look after themselves. It seems to be generally 

 thought that the young are hatched out in the body of the 

 parent, and crawl forth themselves ; but to judge from what 

 has been observed in other ovo-viviparous snakes, this is not 

 really the case. The egg-membranes are complete and un- 

 broken at birth, and the young break through after extrusion. 

 This was certainly the case in three separate instances observed 

 by the writer — two in the rattlesnake, and one in the closely- 

 allied labarria — in each of which more than twenty young 

 ones were thus brought forth. No doubt at the time wlien 

 the young are sufficiently developed and are ready for birth 

 their wriggling movements induce their extrusion, but the 

 eggs are strictly not hatched till afterwards ; and the young 

 can be seen closely coiled inside the transparent membranes 

 until they disrupt them and crawl about. 



It may possibly be the case at times that the adults are 

 placed under conditions not suitable for the bringing forth of 

 the young, and that the latter are then retained until they do 

 actually crawl out; but in the light of the three instances 

 above quoted, this can hardly be regarded as strictly natural. 

 That unfavourable conditions do modify the breeding-habits 

 of snakes is, of course, well known, and a case in point may 

 be given from the egg-laying Aboma {Epicrates). A speci- 

 men which was brought to the Museum some years ago in a 

 closely nailed box was observed at the time to be laying, a 

 few eggs being found in a corner of the box, of which two 

 are still preserved in spirit. The snake was placed in a large 

 wire cage — open to light on all sides — together with a set of 

 reptiles, which included four land- and water-boas, a Teguexin 

 lizard, and an iguana. Some six months afterwards the 

 Aboma was noticed to have brought forth several young ones, 

 which were quite strong and healthy. Whether it was due 

 to the change from the dark box to the exposed cage, or to 



