290 On the Subdivisions of Science 



or, as no such envelope is superadded to the more or less complex ones, 

 furnished by the maternal organism. In the vertebrate amniota, a second 

 foetal envelope, the allantois, is always developed, originating from the 

 anterior aspect of the posterior extremity of the trunk as a body, which 

 is at first bilobed and solid, but which subsequently becomes hollow in- 

 ternally, and covered externally with vascular ramifications, whereby in 

 reptiles and birds the respiration, and in mammals both the respiration 

 and the nutrition of the developing embryo are provided for. From their 

 possession of this structure, the amniota are also known as 'allantoidea'; 

 and as gills are never developed upon their bronchial arches, they are 

 also called 'abranchiata,' whilst the anaraniota have in their turn the two 

 additional names, ' anallantoidea ' and ' branchiata,' as never developing 

 an allantois, at least beyond the stage of a urinary bladder, into which its 

 proximal portion is converted in the higher vertebrata, and as always de- 

 veloping either deciduous or permanent gills." (Rolleston, Forms of 

 Animal Life, Oxford, 1870, p. xxxix.) 



I accept the Dame branchiata or branchiate animals, i. e., 

 animals havinof branchias or irills, for the division anallant- 

 oidea, but I propose the word pulmonata, pulmonates, mean- 

 ing animals having lungs, to designate the allantoidea or that 

 division of vertebrate animals comprising the three classes, 

 mammals, birds and reptiles. I, therefore, divide vertebra- 

 tology into pulmonatology and branchiatology ; and pnlmona- 

 tology into mammalology, ornithology or aviology, and rep- 

 tilology. 



In accordance with the recognized divisions of the mam- 

 malia into placental, marsupial and monotrematous mammals 

 — the first being those whose young, during the period of 

 pregnancy, are nourished by means of a placenta within the 

 uterus itself; the second, those who carry their young in a 

 pouch or bag of the abdomen and nourish them there by 

 suckling, and the third, those who have the generative and 

 renal ducts confluent with the terminal segment of the intes- 

 tine, so as to form a true "cloaca;" — and of the placeutalia 

 into discoplacentalia, zonoplacentalia and villiplacentalia, — 

 depending upon the form and nature of the placenta, which is 

 disk- or cake-like in the first, girdle- or zone-shaped in the 

 second, and made up of scattered papillie or cotyledons in 

 the third; — 1 divide mammalology into placentalology, mar- 



