CHAPTER XXIII. 



PANTOPODA. 



Oviposition and Care of the Brood. The Pantopodan female 

 does not deposit her eggs in the usual manner, but transfers them to 

 the male, who attaches them to his third pair of limbs, the so-called 

 ovigerous limbs (Figs. 74, 3, p. 157), and carries them about until the 

 embryo is mature. The eggs are usually collected into large clumps, 

 containing as many as 100. Several such clumps are found on one 

 male, so that, if Avell laden, he may be found to carry 1000 eggs 

 (Dohrn). Although in such cases, and generally among the 

 Pantopoda, the eggs are very small, they are comparatively large 

 in Pallene (0*25 mm. in diameter), being, for example, 125 times 

 the size of an egg of PhoxichiUdium or Tanystylum (Morgan). 

 Pallene carries only a few glutinous egg-clumps, each containing 

 only two eggs (Dohrn). Nymphon, according to Hobk, has specially 

 large eggs (in N. brevicaudatum, 0*5 to 0*7 mm. in diameter), but 

 yet carries a great number. The large eggs are very rich in yolk, 

 the smaller ones naturally have less yolk. The eggs are spherical, 

 and each is surrounded by a delicate membrane (Fig. 64, D). 



1. Cleavage and Formation of the Germ -Layers. 



The cleavage of these eggs is total (Dohrn, Hoek, Morgan) ; 

 but those genera which have small eggs (e.g. PhoxichiUdium 

 and Tanystylum) show equal cleavage, those with larger eggs 

 (Pallene, Nymphon) unequal cleavage (Morgan). 



Up to the present time but little has been known concerning the 

 early ontogenetic processes in the Pantopodan egg. Many years ago 

 (1843) Kolliker gave an account of the total cleavage of the egg, 

 and Dohrn has more recently described a few stages in the cleavage 

 of the eggs of Pycnogonum that confirm the above conclusion. Hoek, 

 in examining the Challenger material, found a few ontogenetic stages, 

 which, however, could naturally only give a very incomplete idea of 



