REPORT ON THE PYCJSTOGONIDA. 133 



appearance of being surrounded by a very thick and concentrically stratified membrane 

 (ovarian egg oi Nymphon brevicaudatum, PL XXI. fig. 15). In other species [Nymphoa 

 robustum, PL XXI. fig. 16) this membrane is perfectly transparent, while iu both cases 

 tlie granular protoplasm of the egg within this thick membrane or capsule seems to be 

 surrounded by its vitelline membrane. In a third case, which I observed in Nymphon 

 longicoxa (PI. XXI. fig. 17), the membrane of the egg does not seem to be thick, but 

 irregularly folded and crumpled ; yelk-particles are here very numerous iu the central part 

 of the egg, which surrounds the germinal vesicle ; and the protoplasm of the egg extends 

 beyond this central part till it reaches the crumpled membrane. However, it is very 

 probable that the condition of the eggs has suffered from their having been so long in 

 alcohol, only I wish to point out that from what I observed it is almost certain that 

 any one studjdug the formation and the development of the animal egg, will find a very 

 interesting ol^ject in the egg of the Pycnogonida. The dimensions of the mature ova 

 are very different. Of the specimens I studied they are largest in Nymphon longicoxa, 

 N. brevicaudatum, and N. robitshim, a great deal smaller iu N. brachyrhynchus and 

 N. hamatum (the number of eggs united in an egg-mass being always in inverse propor- 

 tion to their size). 



While in the younger ovarian eggs the germinal vesicles as a rule are placed in the 

 centre of the egg, in the very large mature egg the vesicle is placed close to the wall. 

 Sometimes {Nymphon longicoxa) it has the shape of a sand-glass, and once I observed an 

 extremely small micropyle canal in the membrane of the egg, just opposite the place 

 occupied by the germinal vesicle. As a rule there is only one germinal spot, Imt I once 

 observed two distinct spots in the germinal vesicle of the egg of Nymphon longicoxa. In 

 the ovarian egg of Nymphon robustum one distinct nucleolus may be observed almost 

 exactly in the centre of the rounded and granular germinal spot. As for the manner 

 in which the eggs make their way to the genital apertures in those cases in which no 

 true oviduct is observed, I think there can be no doubt that the body-cavity itself per- 

 forms the function of an oviduct. The absence of such a duct at the genital pores, 

 and the fact that I repeatedly observed detached eggs pressed against the connective 

 tissue surrounding the ventral ganglia or other parts in the interior of the body admits 

 of no doubt in this respect. 



All I have said about the ovary and the formation of the ova in the genus Nymphon 

 also holds good in the case of the other genera. The limited quantity of specimens 

 prevented me from making a section of the l^ody of species of these genera. Most 

 probably Ascorchynchits will show the same disposition as Colossendeis. A transverse 

 section of the thigh of one of the legs of Ascorchynchus orthorhynchus is figured in 

 Plate XVI. fig. 11. The thigh is much more dilated than one of the other joints of the 

 leg, yet it is not round but flattened, and the contents are almost divided into two un- 

 equal parts by the large chitinous thickening, which at the one side is in connectio^ 



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