SPINNING FISHES 
5 
F;«TMs-fronds, projecting 8-io inches from the rock, and having 
a diameter in the widest part of 5-6 inches ; or a bunch of 
smaller algae may be chosen, and then the nest assumes a less 
cylindrical and more spherical form, with a diameter of 3-5 
inches. In the former case, little labour is involved, the fish 
merely binding the fronds with threads, which pass round trans- 
versely to the long axis of the mass. When smaller materials 
are used, however, much labour is bestowed upon the structure. 
Here the growing tuft merely forms a foundation on which 
gathered fragments of Ulva, Corallvta, Hydrozoa, &c., are woven ; 
and this heterogenous collection is intermingled with the growing 
fronds and secured by threads, so that it forms a compact mass. 
The materials are often so completely interwoven that it is 
difficult to tear them asunder ; but they are always disposed so 
as to hav^e interspaces, which are enlarged by the fish into 
pocket-like cavities ; and in these cavities one or several females 
deposit the eggs.’ 
Before the observations of Mobius very little was known of 
the nature of the threads ; it was said to be uncertain whether 
they were spun by the male or by the female, and little or 
nothing had been ascertained of the source of the secretion or 
of the organ by which it is emitted. It is true, however, that 
Dr. Heincke, who had observed nests of Spinachia spinachia at 
Kiel and in the Hamburg Aquarium, had suggested that the 
threads came from the urinary bladder" ; and that, in the case 
of Apdtes quad mens, Professor Ryder had given, in 1882, a 
short account of the spinning habits of the male and of its 
threads. 
Confining our attention for the moment to Spinachia spinachia, 
we find that Johnston supposed the building and spinning to be 
done by the female ; Heincke believed the sexes to co-operate ; 
but Mobius and Prince have made it clear that the male alone 
is the builder, and that it is he who spins and surrounds the 
nest with threads. Mobius found that the male continued to 
draw threads round the nest after eggs had been deposited ; and 
in this way the various egg-clusters were over-spun and protected. 
The author figures a nest, which— taken from Kiel Harbour — 
had been placed in an aquarium together with the male to 
which it belonged. There were three egg-clusters, of which the 
uppermost was unprotected and merely rested on the nest ; after 
two days the fish died, but he had managed in the meantime 
to over-spin this egg-cluster, and also to draw some threads 
round the twig to which the nest had been tied. Prince, who 
carefully watched the processes of building and spinning in 
tanks at St. Andrews, states that though females distended with 
ova often hovered near during the construction of the nest, not 
' E. E. Prince, “On the Nest and Development of Gastrosteus spinachia," 
Annals and Magazine of Natural History (5), xvi. (1885), pp. 487-96. 
’ F. Heincke, 1882 ; quoted by Mobius. 
