: “ . 
136 THE VOYAGE OF H.M.S. CHALLENGER. 
in Ascorhynchus minutus, one packet only on each ovigerous leg. I believe, however, 
that cases are by no means rare in which two or even three packets are formed on one 
ovigerous leg... The packet is placed round the leg, and in some species (Nymphon 
brachyrhynchus, Hoek, e.g., Pl. XIX. fig. 1), it may be easily brushed off. In other 
species, however, Nymphon robustum, Bell, for example, this is by no means so easy, the 
surface of the joints of the ovigerous legs being furnished with numerous hook-like 
spines. 
Every egg in the packet has its own membrane, a very thin and structureless tunic. 
The size of the packets is very different. It varies greatly with the size of the animal, 
but is different also in different specimens of the same species. The size of the egg 
seems to be constant for every species ; consequently the size of the packet will depend 
on the number of eggs in each packet ; and the age and the condition of the female will, 
of course, influence this. 
The egg of Nymphon brevicaudatum, Miers, measures 0°5 or 0°7 mm. ; when in the 
first stages of development it is nearly globular (0°6 x 0°6 mm.), afterwards oval (0°5 x 0°7 
mm.). The number of eggs in each packet varies between fifty and sixty. The egg 
of Nymphon fuscum is a great deal smaller (0°15 or 0°12 mm. The eggs of Nymphon 
brachyrhynchus are about 0°55 mm. and even in a much advanced stage of development 
nearly globular. Large packets of the latter species do not contain more than fifty eggs, 
and the dimensions of these packets vary between 3°14 x 1°85 mm. and 2°3 x 1°6 mm. 
The ege of Nymphon brevicollum has a diameter of 0:26 mm.; the number of eggs in a 
packet is in this species about ninety. Fig. 2 on Plate XIX. gives a section of a 
packet of eggs of this species. The colours are those which are seen when the 
object is coloured with picrocarmine, and the figure is half in outline ; every egg is seen 
to be placed in a cavity formed by the cement which solders the eggs together (c), and 
- coloured distinctly red by the, picrocarmine. The large opening (0) in the centre is 
that occupied by the ovigerous leg ; the small holes (s, s) are those which are left between 
the eges when soldered together. On the outside mud and sand particles adhere to the 
packet (m). 
So far as I know, Dohrn is the only author who has published observations on the 
cleavage of the Pyenogonid egg ;' but as the method of making sections of such very 
small eggs was not yet in use when he published his paper, and could not, theréfore, 
he applied by him, I might reasonably have expected to see much more than he did, by- 
availing myself of this method of recent embryology. Yet my researches in this respect 
were not very successful, owing at least partly, I believe, to. the condition of the material 
I studied. Every one will acknowledge how necessary it is, especially in embryological 
researches, to study fresh and also very rich material ; now the Challenger Pyenogonids 
had been six or seven years in alcohol before I studied their eggs, and, moreover, the 
1 A. Dohrn, Ueber Entwicklung und Bau der Pycnogoniden, Jenaische Zeitschrift, Bd. v., 1869. 
