PYCNOGONIDA. 21 
is shown by the series of larval forms, given in the following figures 8—11, and 16—17 of Pseudo- 
pallene spinipes and circularis, as well as of Pa/llene brevirostris; as they, however, belong to the se- 
cond larval stage, they will be mentioned more in detail in a following section. It may be possible, 
of course, that I can have overlooked rudimentary larval legs; but in a somewhat later stage of the 
same species I have seen no trace of these legs either, and as, in all places where I have observed 
them, they have only appeared as one or two pairs of short, inarticulate processes, I am inclined to 
suppose that here they have been quite absent. Of still less importance is the peculiarity that the 
foremost pair of ambulatory legs have begun to appear so early, before the chelifori were quite 
developed, and before the byssus-gland was formed. The two genera mentioned here must be supposed 
to pass a great part of the second larval stage in the egg-shell. 
Morgan, Contrib. Embryol. 1891 has not in 2a//ene empusa seen any trace of the foremost pair 
of the embryonal legs, though he has seen some trace of the second pair; at all events I understand 
the following quotation in that way, 1. c. p.14. «On the sides of the body, just in front of the first 
pair of ambulatory legs, are a pair of projections, one on each side. These are the beginning of the 
third pair of limbs — the ovigerous legs. I have seen no traces of the second pair of appendages in 
the ontogeny of Pallene». 
In the basal part of the chelifori is most frequently found a large gland, the 
byssus-gland, with an excretory duct opening through a shorter or longer hollow 
thorn in the fore-margin of the said basal part. 
The occurrence of a large gland in the chelifori has already been mentioned by Dohrn and 
Hoek, who have also given descriptions and figures of it; by Morgan it is only drawn in the che- 
lifori of 7aønystylum orbiculatum; cp. the following. 
This gland, the byssus gland, is most frequently distinetly conspicuous, and through the 
epidermis it is seen to consist of a circle of large glandular cells gathered round a hollow, or reser- 
voir, from which an excretory duct is seen to lead to the inner fore-end of the basal part of the 
cheliforus, comp. the enlarged figure of the fore-end of the larva of ymprhon grossipes, pl. I, fig. 22. 
In Nymphon elegans, pl. 11, fig. 16, I have found the gland to be almost as distinct and of the same 
structure; while it was far less distinct in Nymphon longitarse, pl. II, fig. 19—20, Nymphon,robustum, 
pl. II, fig. 6, Nymphon macronyx, pl. 11, fig. 11, and in Nymphon spinosum, pl. 11, fig. 13; but possibly it 
was not quite developed, and so was not so well preserved in the spirit. The excretory duct opens 
into the basal end of a shorter or longer hollow thorn, through the point of which the gland-secretion 
is produced as a very thin thread of a considerable length. The thread, which stains strongly (I have 
in all instances used picro-carmine), is easily seen, and is also to be seen in my figures of the larvæ. 
The development of the gland begins very early in the embryonie stage on the border of the basal 
end of the cheliforus and the corresponding metamere, but it is not finished until later in the first 
larval stage, when the larva has left the egg wholly, or, at all events, with the fore part. The length 
of the excretory thorn varies very much; generally it is short or even very short, but it can, as in 
Pycnogonum littorale, gain a very considerable length, about the length of the embryonal legs, cp. pl. I, 
Fr] fig. 3, where, however, the limit between the thorn and the free thread, which limit is difficult to see, 
has not been indicated. The genera, in which I have found a distinct gland with a thread arising 
