GROWTH AND EEARING OP FOOD-FISH. 373 



aud tlie present species probably spawns about the same time, so 

 that the young specimens obtained from Sutton Pool were probably 

 three or four weeks old. They were placed with the young 

 flounders, and throve well, feeding on the chopped worm supplied to 

 the latter. One killed on August 19th was 3| inches long (7"9 cm.). 



Grey Mullet [Mugil chela, Cnvier). — Last year a number of the 

 young of this species were brought to the aquarium by M r. W. Bateson, 

 and are mentioned in his paper in the previous number of this 

 Journal. These little fish were taken in the open sea, but there can 

 be no doubt that they were hatched the same year, though in which 

 month it is not easy to decide. When obtained by Mr. Bateson in 

 July and August they Avere about f of an inch long. I obtained 

 some of the same species this year in Cawsand Bay on May 14th, 

 which were 11 mm. (y^g- inch) in length. These were, in all proba- 

 bility, from their almost larval appearance, not more than one month 

 old, so that probably the species spawns in April. 



Some of Mr. Bateson's specimens have been living in the aqua- 

 rium tanks up to the present time (August, 1890). One of these 

 killed on August 25th measured 5" 7 cm. in length (2^ inches). 

 Another specimen, brought in from the sea this year, is somewhat 

 larger, but not more than 3 inches long ; this specimen is doubtless 

 also in its second year, and has probably grown a little more in its 

 free condition than the captive specimens. 



Both these young mullet and the adults in the tanks are fond of 

 a kind of food which no other fish has ever attempted to eat, namely, 

 the dirty-looking, fleecy vegetable growth which covers the sides 

 of the tanks and the rock-work.* I have watched both the young 

 and old individuals browsing almost like cattle on this growth. The 

 stuff is of a dark brown, almost black, colour, and has a ragged 

 offensive appearance. Examined by the microscope it was found to 

 consist chiefly of Diatomaceae. It was composed of interlacing 

 filaments, formed by the filamentous species of Diatoms, covered by 

 sessile or separate forms ; among the Diatom filaments were also 

 some others belonging to another class of Algge, the Cyanophyceae ; 

 these resembled the genus Tolypothria , and were of a bluish-green 

 colour. (The plants were examined by Professor T. Johnson, who 

 is at present studying at the Laboratory.) This vegetable growth 

 was found in abundance in the stomach and intestines of the young 

 mullet killed on August 25th. It is somewhat surprising to find a 

 fish, which belongs to the highest class of animals, living directly on 

 Diatoms, which are among the most lowly organised of plants. 



The mullet in our tanks will eat sparingly of other kinds of food, 



* This growth occurs also in other .nqnaria; for instance, at Amsterdam and at tlie 

 Crystal Palace.— Ed. 



