192 On the Development of the Pycnogons. 



females, whilst in others (according to Kroyer) both males 

 and females possess them. 



These false feet, or egg-carriers (for no other office has 

 been assigned to them), are jointed limbs, produced from the 

 anterior portion of the thorax, between the origin of the ros- 

 trum and the first pair of legs; the number of joints of which 

 they are composed varies in different genera, and affords a 

 generic character in the case of Fallene and Phoxichilidium : 

 the former having nine or ten joints, and the latter only five. 

 The ova, which are found in masses of a globular form, to 

 the number of two or three, are attached to these limbs ; the 

 limb usually passing through the centre of the globular 

 mass. At the earliest stage at which the ova has been exa- 

 mined, they are merely little granular bodies, each the -3-15-0 th of 

 an inch in diameter, or thereabouts, according to the relative 

 size of the species producing them. 



The " oviferous mass" is composed of a large number of 

 these ova, and invested by a tough skin, which nevertheless 

 admits of extension during the enlargement of the granules. 

 It seems highly probable that the earliest stage of this mass is a 

 single germ, which undergoes segmentation, and resolves itself 

 into a number of independent ova. This view is suggested 

 by the fact that in early stages the oviferous mass is a hard 

 ball, consisting of a number of closely compressed ova, which 

 by degrees assume a globular form, and then separate from 

 each other ; and further than this, each ovum is attached by 

 two or more filaments to the skin, which invests the whole, 

 proving that it has a close and intimate connection therewith. 

 But how this oviferous mass becomes attached to the false feet 

 or " egg-carriers," no one has been able to discover, nor even 

 surmise. The development of these animals in their earliest 

 stage is consequently involved in obscurity. 



Various observers have recorded the result of their ob- 

 servations respecting the earliest stage of several species. 

 Kroyer has, however, done more than any one else, for he 

 figures several stages;* whereas other writers have merely 

 recorded their observations on the stage immediately after 

 quitting the egg. 



I have only been fortunate enough to trace out the entire 

 development of two species (Phoxichilidium coccineum and a 

 species of Nymphon) ; but they present such totally different 

 results that neither can be taken as a type of the develop- 

 ment of the order, and it seems highly probable that each 

 genus will be found to vary considerably from those associated 

 with it. 



* Sur les Metamorphoses des Pycnogonoides. Par M. Kroyer. Ann. des 

 Sciences Naturelles > 1842. M. Kroyer in Gaimard's Voyages en Scandinavia. 



