- 59 - 



manner of propagation. The female deposits her eggs on coral 

 branches, or on plants or rocks. The eggs are single square, horny, 

 transparent capsules, which are first white and then turn into a 

 yellowish brown colour; they have at each corner long twisted 

 cartilaginous strings similar to cat-gut, by means of which the 

 female fastens each egg to some object , and to effect this , 

 swims round and round it while the egg is being ejected from 

 her body. This hanging-up of the egg is meant to preserve it 

 from being covered by mud or sand , which is the greatest 

 danger to which it is subject, except that of being destroyed 

 by the animals that live in the sand. The development of the 

 germ in the egg can be well seen through the transparent shell. 

 The so-called germ-spot first develops on the oval yolk , and 

 gradually over-grows and becomes separated from it. Later on 

 one can recognise the form of the little fish which is transpa- 

 rent as glass , and has on each side of its neck a bunch of 

 exterior gill-threads (temporary embryonic organs). It is con- 

 nected with the yolk-bag by a long string which conducts the 

 nourishment into its intestine. The lively undulating move- 

 ments of the slowly growing little animal can now be seen ; 

 by-and-by the gill-threads are absorbed , and later on , the 

 colouring and spots on the skin of the young fish gradually ap- 

 pear and increase in distinctness. When the young one is ready 

 to escape from its prison, and has consumed all the yolk, it 

 pushes itself head-first through one end of its eggshell where 

 the flakes are more loosely connected , and swims actively 

 about, dragging after it the remains of the yolk-bag. The eggs 

 and embryos are often to be seen in the Aquarium , for not 

 only as the Scyllii of the large tank pair and deposit their eggs 

 on rocks and branches, but fishermen also bring pieces of coral 

 and similar objects hung with shark-eggs. Just lately these 

 embryonic stages have become very important to science, and 

 comparative anatomy has very often profited by the rich ma- 

 terial afforded by the Zoological Station. The use of the Scyllii 

 from an economic point of view, is very small. Their flesh is 

 bad , and only eaten by the very poor ; the skin is used for 

 polishing, the liver for preparing oil. They commit great rav- 

 ages among herrings in the northern seas. 



The smooth shark of Aristoteles, Mustelus laevis, is far 

 less often found in the Aquarium than the cat-shark , for it 

 can scarcely endure confinement. It is one of the most harm- 

 less of the race. Its blunt teeth oblige it to feed on mollusks 

 and other soft animals, which it finds in the deep sea. When 



