MONOTKF.MATA. 



399 



tical membrane it is probable that this does not 

 become organized into a placenta, and that the 

 Monotrewuta like the Marsupiata are essentially 

 ovoviviparous. Since, however, the female Or- 

 nithorhynchus has no tegumentary pouch to pro- 

 tect a prematurely born offspring, it must be pre- 

 sumed that the foetus acquires greater propor- 

 tional bulk* and more mature strength by a 

 longer continuance within the uterus. In this 



respecting the young Ornithorhynchus, pro- 

 bably not long excluded from the foetal enve- 

 lopes, by an examination of two specimens, 

 obtained by Lieut, the Hon. Lauderdale Maule, 

 from two different nests, discovered by him in 

 the banks of the Fish River, Australia, and 

 presented by Dr. Weatherhead to the Zoolo- 

 gical Society of London. 



Subjoined is an outline of the smaller of 



195. 



case it may be doubled whether the vilellme these specimens of the natural size (jig. 19.5). 

 vesicle will suffice for nourishment and respi- 

 ration through the whole period of develop- 

 ment, and the allantois and umbilical vessels 

 will probably be more expanded for that pur- 

 pose. 



The means of prosecuting this inquiry are 

 the more likely to be afforded, since, through 

 the exertions of Mr. Bennett, the period when 

 the pregnant female may be procured is now 

 ascertained. Had not a specimen, supposed 

 to be in this condition, which my friend had 

 obtained alive, unfortunately escaped from its 

 confinement, he would, there is little doubt, 

 have ascertained the true nature of the gene- 

 rative product, and the probable duration of 

 gestation. 



With reference to the latter point, Mr. Ben- 

 nett observes, that two months after the cap- 

 ture of the female specimen with the smallest 

 ova, viz. on the 8th of December, 1832, he 

 succeeded in laying open one of the burrows 

 of the Ornithorhynchi on the banks of the Mur- 

 rumbidgee River, in which three living young 

 ones were found : they were naked, and mea- 

 sured only one inch and seven-eighths in 

 length, and he considers them to have been 

 recently brought forth. Not having any means 

 of preserving these specimens, and being at a 

 great distance from Sydney, they were lost. 

 The nest was most carefully scrutinized by 

 Mr. Bennett, but not the slightest trace of an 

 egg-shell could be perceived in it. 



The principal points, therefore, in the ge- 

 nerative economy of this paradoxical species 

 which still remain to be determined by actual 

 observation are 



1st. The manner of copulation. 

 2d. The season of copulation. (This is pro- 

 bably at the latter end of the month of Sep- 

 tember or beginning of October.) 



3d. The period of gestation. (This is pro- 

 bably six weeks.) 



4th. The nature and succession of the tem- 

 porary structures developed for the support of 

 the foetus during gestation. 



5th. The exact size, condition, and powers 

 of the young at the time of birth. 

 6th. The act of suckling. 

 7th. The period during which the young- 

 requires the lacteal nourishment. 



8th. The age at which the animal attains its 

 full size. 



I have ascertained the following particulars 



Larger 

 Orniiho- 

 rhynchus. 



In. L. 



6 6 



4 



4 



1 



8 







* In reference to this point it may be observed, 

 that the kidneys are not lodged low down in the 

 pelvis as in the true Ovipara, but occupy the posi- 

 tion characteristic of the Mammifcrous type of 

 structure, which allows free space for the enlarge- 

 ment of the uterus during pregnancy. 



Young Ornithorhynchus. (Original.) 



The following are admeasurements of these 

 two specimens : 



Smaller 

 Ornitho- 

 rhynchus 

 In. L. 



Length from the end of the 

 upper jaw over the curve 

 of the back to the end of 



the tail 3 9 



Length from the same points 

 in a straight line along the 



abdomen 2 1 



Greatest circumference of the 



body 2 9 



Length of the head 8J 



Length of the upper man- 

 dible 3 



Breadth of the upper man- 

 dible at the base 4 



Thickness of the upper man- 

 dible at the anterior margin 0: 

 Length of the lower mandible 2 

 Breadth of the lower man- 

 dible at the base 3 



Length of the tail from the 



vent 



Breadth of the tail at the root 



Length of the fore foot 



Breadth of the fore foot. . . . 

 Length of the hind foot. . . . 

 Breadth of the hind foot . . 

 Distance between the eyes. . 

 Distance between the nostrils 

 From the exterior nostrils to 



the end of the mandible 1 02 

 From the tip of the tongue 

 to the end of the lower 

 mandible 0} 0. 



5 



6 



1 



1\ 



5 







































4 

 3 



3i 



4 



3 



3 



H 



o 





 

 

 

 

 

 



10 

 8 

 5 

 5 



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