

DEVELOPMENT OF L1SSENCEPIIALA. 731 



killed June 20, had a single foetus, half an inch in length. A 

 female of Vespertilic noctula produced, on the 23rd June, a young 

 one, with an umbilical cord two inches in length. 1 Judging from 

 observed dates of pairing, the gestation seems to be about forty 

 days. The chief difference from Insectivora is in the larger propor- 

 tion of the placenta formed by the long arborescent villi organised 

 by the allantoic vessels: the reduced decidua beyond the ma- 

 ternal cake may be traced over a great part of the chorion, which 

 receives, as in other Lissencephala, vitelline vessels. 2 



According to Cams, 3 the placenta of the Ai (Bradypus tridac- 

 tylus) is divided into so many distinct lobes, as to resemble the 

 cotyledonary condition of the placenta in most Ruminants : but 

 there are no corresponding partial thickenings of the lining sub- 

 stance of the uterus like the maternal cotyledons shown in fig. 546. 

 The so-called placentulse, of an irregular oblong, subdepressed 

 form, from 1^ to less than ± an inch in diameter, and from 30 to 

 40 in number, project from the endochorion, or inner surface 

 of the allantois, into the interior of that sac : they are richly 

 supplied with allantoic vessels : their flattened outer surface .ap- 

 plied, with the uniting layer of chorion, to the inner surface of 

 the uterus, may receive therefrom a medium of ramification 

 of maternal vessels, answering to a decidua scrotina. The pro- 

 bability indeed is, that maternal deciduous substance is inter- 

 blended with such allantoic lobules of the Sloth, as is the case 

 with the single thin oblong placental disc in Dasypus. The 

 genus Manis offers a third instance of the extent to which the 

 temporary structures developed for the behoof of the foetus, and 



1 The mother gnawed the cord across and ate the afterbirth. 



2 A critic of xx. vol. v. pp. 140-45, writes : — ' The delicate arborescent appearance 

 which is described in the placenta of Pteropua is due, in all likelihood, to the prolonged 

 maceration in spirit,' &c. ccxxvn". p. 310. The Hunterian preparation yielding, ac- 

 cording to the Oxford Professor, the above description (No. 3579, Physiol. Series) is 

 well placed for illustration of this alleged influence in the production of modifications 

 of placental structure. Some of the specimens had been put into spirit in 1754, thirty 

 years before the placenta of the Pteropus was so treated ; and both, together with other 

 Hunterian preparations of placentae, have been since subject to eighty years of ' macera- 

 tion in spirit ! ' But there was really no need to assume so special a behaviour of 

 a Bat's afterbirth under maceration, in order to show that ' this placental peculiarity 

 brings them, as Linnaeus did bring them, into the same class as the Primates' (ccixvii". 

 p. 310). No one, now, dreams of leaving Bats among birds. Perhaps, however, Dr. 

 Rolleston may mean the same order in the mammalian class. But cerebral, circulat- 

 ing, osseous and generative characters, especially those of the male organs, were even 

 the placental structures so similar to human ones as Dr. E. contends, w r ould outweigh 

 them, and I believe will guide all unprejudiced naturalists in juxtaposing the winged 

 with the terrestrial Insectivora, and in relegating both to the low lissencephalous 

 subclass. 



3 xliii. p. 21, tab. ix. figs. 15-17. 



