36 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 



TABLE OF COMPARISONS. 



In the following table I have collected fourteen characters relating to the sexual 

 and reproductive characters of the four known subgenera of Peripatus. It is thought 

 that the presentation of these facts in a compressed form may be acceptable to the 

 reader. (For other external characters, see the early part of this memoir.) 



It is necessary to add a few explanatory notes to the table. 



i. I do not know whether the egg-membrane of P. novae-britanniae corresponds 

 with the chorion or with the vitelline membrane of the Cape and Australian species. 

 I think it corresponds with the chorion. It is possible that specially directed investigations 

 might result in finding a thin vitelline pellicle below this membrane in the unsegmented 

 ovum, or even during the early segmentation stages. It is certainly not present in my 

 Stage III. 



ii. The egg-membrane persists beyond Stage X, but I have not found it in my 

 oldest embryos. In P. capensis the chorion persists until birth (Sedgwick), as also in 

 P. leuckarti (Steel). 



iii. In P. novae- zealandiae the young are white at birth, but the antennae are 

 slightly tinged with purple (Hutton). 



In P. capensis the young at birth are either quite white or of a diffuse reddish 

 colour ; only the antennae are green (Sedgwick). 



iv. With regard to the mode of fecundation. At a meeting of the Linnaean 

 Society of New South Wales, which I attended in Sydney in 1896, I heard Mr Steel 

 describe copulation as occurring in P. leuckarti, but for some unaccountable reason 

 the observation is not recorded in the paper by him which I have cited more than once. 

 Its occurrence in P. novae-britanniae is rendered especially probable by the presence of 

 the external muscular male papilla. Finally, it is a priori probable that it occurs in all, 

 except in Peripatopsis, on account of the presence of a pair of specially differentiated 

 receptacula seminis. 



v. Crural glands could not be included in the above table because, while they 

 occur in P. leuckarti, they are absent from P. novae- zealandiae. As mentioned already, 

 there are none in P. novae-britanniae. 



vi. Steel has observed that the young of P. leuckarti measure 5 mm. at birth, 

 and during the first 12 months the rate of growth was rather less than 1 mm. a month. 

 He estimates that a female takes upwards of two years to reach maturity, and thinks it 

 probable that the birth of young does not commence until the mother is three years 

 old. 



vii. It will be observed that the embryos of P. novae-britanniae and of the 

 subgenus Peripatus s. str. are born in a more complete condition than are those of the 

 other two subgenera. In other words, the viviparity is more complete. I should think 

 the less complete viviparity of the latter forms is not a primitive feature. 



