SFAKE-IXCUBA TION. 



479 



New World species have been examples of this ; 

 as, for instance, the " garter-snake," the " chicken- 

 snake," and the " yellow boa " of Jamaica (Chi- 

 lobothrus inornatus), the latter on several occa- 

 sions, and sometimes depositing eggs at the same 

 time, but the eggs proving bad. 



Mr. Philip Henry Gosse, when in Jamaica 

 nearly thirty years ago, gave much careful atten- 

 tion to the habits of this " yellow boa," a snake 

 which sometimes attains eight or ten feet in 

 length and is extremely active. He records a 

 great deal of highly-interesting matter concerning 

 the chilobothrus ; and, as a careful and conscien- 

 tious observer, his testimony is of much value. 

 That this snake when at liberty lays eggs was 

 well known, nests with eggs in them being often 

 found. In one case a "yellow boa" was seen 

 issuing from a narrow passage in a bank, which 

 when dug into was found to lead to a cavity 

 lined with leaves and soft trash, and containing 

 eggs. This hole had been excavated, because the 

 dry, crumbled earth was discharged at the en- 

 trance, where it lay in a heap. The passage was 

 only just large enough to admit the snake, and 

 the soft rubbish within must have been carried 

 there. We cannot positively assert that the 

 snake constructed this skillful hiding-place for 

 herself, but, if she did, she must have forced out 

 the earth as the burrowing snakes do, or by the 

 muscular undulations of her body ; and she 

 must have conveyed the leaves there in her 

 mouth. Snakes do, we know, sometimes make 

 nests by coiling themselves round and round to 

 form a hollow. Under either circumstance ma- 

 ternal instinct is undeniable ; and, if chilobothrus 

 merely discovered and appropriated the nest of 

 some other creature, her intelligence is still 

 worth recording. 



We know an instance where a snake, in cap- 

 tivity exhibited restlessness and uneasiness, crawl- 

 ing about the cage as if in search of something. 

 Those who had the care of it suspected she was 

 with eggs, and placed some sand in the cage. 

 This appeared to satisfy her, and the eggs were 

 deposited. Mr. Gosse had a Jamaica boa in the 

 same condition. For a long time it manifested 

 discomfort and restlessness, being savage and in 

 every way objectionable, till at length it pro- 

 duced a family of young ones. Knowing it was 

 the habit of this snake to incubate its eggs, Mr. 

 Gosse was greatly surprised at the event; and 

 the startling question occurred to him that, when 

 circumstances are unfavorable for the deposition 

 of eggs, could a snake retain them until the 

 young are hatched ? 



Mr. Gosse's surmises have been entirely con- 

 firmed both by similar occurrences at the Zoologi- 

 cal Gardens and by other writers, who in the sub- 

 sequent interval have also given careful attention 

 to the habits of Ophidians, and have produced val- 

 uable scientific works on the subject. It is now 

 an ascertained fact that not chilobothrus only but 

 several other oviparous species may at pleasure 

 be rendered viviparous by retarding the deposi- 

 tion of their eggs when circumstances are unfav- 

 orable for them ! In fact, we find that we must 

 almost discard those old distinctions of oviparous, 

 viviparous, and ovoviviparous — which German 

 authors tell us are not founded on any other 

 ground than a greater or less development of the 

 foetus in the egg at the time of laying ; or on the 

 nature of the exterior covering of the egg, which 

 is thicker and leathery in those which take some 

 time in hatching, and slighter and membranous 

 in those which are hatched either before or on 

 deposition. 



In serpents the eggs differ from those of birds 

 by undergoing a sort of incubation from the very 

 first, so that, whenever examined, the embryo more 

 or less advanced will be found. In the case of the 

 pythoness in 1862, an egg was examined on the 

 fifteenth day of incubation, and found to contain 

 a living embryo ; a noteworthy fact, as the python 

 incubates for fifty-six days before hatching her 

 eggs. Observations with the eggs of chilobothrus 

 are attended by the same results — namely, the 

 foetus in a certain stage of development is discov- 

 ered whenever a gravid snake is killed and exam- 

 ined. The young ones of the boa in the London 

 collection were perfectly developed and active, 

 climbing all over their cage as soon as they saw 

 daylight. One family consisted of thirty-three; 

 another of eight ; and another of fourteen. The 

 activity and daring of the snakelings were amaz- 

 ing, affording ample proof of their perfect devel- 

 opment. They were always on the defensive, 

 showing fight on the slightest molestation. When 

 the keeper put his hand into the nest among them 

 they seized upon it, and held on so tightly with 

 their teeth that on raising his hand they hung to 

 it, wriggling and undulating like a waving golden 

 tassel. I ventured to take up one of these aggres- 

 sive little reptiles, but could scarcely hold it, from 

 its energetic wrigglings and contortions. It con- 

 stricted my fingers tightly enough to prove its sin- 

 gular instincts, and bit me savagely with its sharp 

 little teeth ; but, my glove being on, I permitted 

 this, glad of so good an opportunity for making 

 personal observations. 



It was said of the python that, notwithstand- 



