704 PERIPATUS. 



both in its structure and habits. While abundant moistui'e is absolutely indispensable 

 to its existence, immersion is quickly fatal ; it is therefore likely to prove of peculiar 

 theoretical value to the zoogeographer since the only conceivable means of transit from 

 one place to another is by land. But the occurrence of distinct geneiTi in Australasia 

 (Australia, Tasmania and New Zealand), in New Britain and in the Malay Peninsula 

 and Sumatra, rendere it impossible, in the absence of information concerning the 

 representation of Peripatus on any of the intervening islands, to consti'uct a scheme of 

 any route of migi-ation in former geological ages, especially as we cannot be certain 

 whether the centre of distribution lay in the Eastern or the Western Hemisphere, 

 although M. Bouvier' is of opinion that the American Continent was the original head- 

 quarters of the Onychophoran stock. 



lentil quite recently a peculiar correlation has seemed to subsist between three classes 

 of phenomena in their relation to Peripatus, namely: (1) the discontinuity of its areas of 

 distribution : (2) the generic divergence of the different tj'pes ; (3) the method of nutrition 

 of the young in the intra-uterine development. 



It now appeal's certain that this con-elation is neither so simple nor so fixed and 

 definite as had been supposed. If the method of embryonic nutrition, for example, were 

 strictly correlated \\'ith the generic divergencies, the selection of any particular method as 

 bearing a more primitive or ancestral stamp than the rest, might well appear arbitrary-, 

 since the generic divergence may be taken to depend partly upon the discontinuity of 

 distribution. 



When I firet became acquainted with the blastodermic or trophic vesicle of the 

 embryos of the New Britain species {Parapeftnpatus novae-britanniae) I was completely at 

 a loss to offer any provisional explanation of it based upon morphological principles, but 

 in the course of time I evolved a working h\-pothesis, an account of which was published"-. 



Through the kindness of Professor G. B. Howes, F.R.S., I have recently come to the 

 knowledge of an interesting memoir by Dr H. J. Hansen of Copenhagen, on the stnicture 

 and development of a primitive insect named Heinimerus talpoides, belonging to the order 

 Orthoptera'. This insect has been found living in the fur of a West Afiican rat of the 

 genus Cricetomys : it resembles a wingless cockroach ia supei-ficial appearance but is more 

 nearlv related to the Forficulina than to the Blattina. as is indicated especially by 

 the aiTangement of the mouth-parts. The chief peculiarity of Heinimerus lies in its 

 anomalous method of propagation which isolates it fi-om all kno\\"n insects. It is truly 

 \i\-iparous (not merely ovoviviparoiis) and in one female Dr Hansen foimd six embryos 

 at different stages of development, the largest of which, in its convoluted state, measured 

 2'8 nun. in length and the smallest 1'2 mm.^ 



Dr Hansen points out that it is thus evident that Heinimerus gives birth to its 

 voung singly and in succession, not simultaneously; moreover the newly born 3'oung onl}- 

 differs fi-oni the adult in the less number of joints of the antennae and in lacking 

 the sexual modification of the posterior abdominal segments. 



' Zool. Anz. XXIV. 1901, p. .5'.t. 



-■ \Yilley, A., " Tiophoblast and Serosa." A contributiou to the morphology of the embryonic membranes 

 of insects. Quart. J. Micr. Sc, Vol. 41, 1899, pp. 589—609. 



^ Hansen, H. J., " On the strncture and habits of Heiiiimenis talpoides Walk.," Eiitomol. Tidskr. xv. 

 Heft 1, 1894, pp. 65—94, Pis. 2 and 3. 



■• The length of the parent without the cerci was 11-5 mm. [Hansen.] 



