22 PYCNOGONIDA. 
from it, are Nymphon, Pycnogonum, Pseudopallene, and Pallene. In the last-mentioned genus, however, 
I have in Fa//. brevirostris found, in stead of a single thread originating from the common gland, a 
bundle of seven, rather short, somewhat curled threads each issuing from an excretory duet of its 
own, pl. I, fig. 16 and 17. I have seen no gland from which any of these threads might arise; but I 
think it also probable, in comparison with what Hoek has found in Wymphon hamatum, what I shall 
presently recur to, that each of the seven threads arises from a cell of its own. In 2-%oxichilidmem 
femoratum I have found no trace of these glands, nor of their thorns and threads; the threads drawn 
on pl. I, fig. 4, are the outermost joints of the embryonal legs, which are prolonged in a bristlelike 
manner, and probably replace the wanting byssus-threads; this larva, with its parasitic way of living, 
has no use for the hooks, to which in the other Pycnogonida the outermost joint of the embryonal 
legs has been transformed. In Paranymphon spinosum”), pl. II, fig. 22—24, I have found indistinct 
traces of the gland and excretory duct, and the thorns were long and closed. In Zezes /uspidus, pl. II, 
fig. 27, I have found a distinct gland, but no excretory duct from it, and also here the thorns were 
closed. It may be possible that in the two last-mentioned cases a reduction of a commonly occurring 
organ has taken place, as it would seem to be natural in 2xoxrchilidium; but it may also be supposed 
that we have here a stage of transition from a simpler organ to the more perfect byssus-gland. 
Dohru and Hoek have already earlier described and drawn this gland, and Dohrn espe- 
cially, in Bau u. Entwick. Arthrop. 1870, has from the larva in the first stage of Åchelia lævis (= 
Ammothea lævis) Taf. V, fig.7, given a figure of the gland with its excretory duet and a secretion- 
thread (byssus) projecting from the long, pointed, hollow thorn, but from Pycrogonum littorale in a 
similar stage only the hollow thorn, he, as it would appear, not having seen the thread, not to speak 
of the gland. In the text he, when speaking of Åchelia lævis, describes the gland rather copiously, 
but says nothing of its use or importance, 1.c. p.141 seq. Hoek, in «Report Pycnog. «Challenger»,» 
1881, draws this gland in Wymphon brevicollum and N. longicoxa, pl. XX, fig.2 and 5, and names it 
in the explanation to the plates «Spinning apparatus in the mandible». Im another Wymphon, N. 
hamatum, pl. XX, fig. 3 and 4 he draws, instead of the common gland, a whole heap of single miliary 
gland cells each cell with its own secretion-thread. No doubt this last form of glands with its threads 
corresponds to the bundles of threads I have mentioned in Fa//ene brevrrostris; and as in the last- 
mentioned species the gland was different in structure from that of the other species of the same or 
of nearly related genera, so is also the structure of the gland in Wymphon hamatum peculiar, compared 
with that in all the many species of Wymphon, from which the gland is known. Hoek in his text, 
l.c. p. 141, compares the secretion-threads to the byssus-threads of the Lamellibranchiata, which com- 
parison I have found so appropriate that I have given to the gland itself the name of «byssus-gland». 
Dohru generally draws the byssus-gland of the larvæ of which he gives figures, but he does not 
always indicate it by special letters; when he does so, he gives the letters /7/, which in the explan- 
ation to the plates are rendered as «Hautdrisen», and ZÆ//D, which are rendered as «Ausfuhrungs- 
gang der Hautdrusen». In the text they are mentioned in the section entitled, «Geschlechtsorgane 
und Entwickelung», especially on p.70 seq., and here Zarana arenicola is also pronounced destitute 
1) Cp. the note on p. 14. 
