PELAGIC FAUNA. 37 



and later condition as they descend. The enormous numbers, 

 countless variety, and ever-changing nature of the small animals, 

 either directly or indirectly constituting the food of these little 

 fishes, form an important feature in the economy of the sea. 

 Now it is the arrow-like Sagitta that fills the tow-nets to 

 bursting, now Appendicularians, again the Cydippe-group 

 or Crustaceans (Thysanopods). Such animal forms comprise 

 those long known in the British seas, besides others more 

 familiar to arctic voyagers, or to the sunny waters of the 

 Mediterranean, for with modern apparatus and persistent 

 effort (thanks hitherto, at any rate, to the enlightened views of 

 the Government acting through the Fishery Board) our 

 knowledge is always extending. 



It is a remarkable fact that it is primarily to plants in 

 inshore waters that the abundance and variety of animals are 

 in many respects due, especially if estuaries also debouch in 

 the neighbourhood. Thus nowhere are the swarms of Sagittce, 

 Appendicularians, Crustaceans, and other forms of fish-food 

 more conspicuous than in the midst of a sea teeming with 

 diatoms, Rhizosoleniae, and other algoid structures ^ These 

 nourish many of the lower forms upon which the crustaceans, 

 annelids and other higher types feed, the latter again falling a 

 prey to the fishes. Moreover, while the larger forms of the 

 Copepods and other crustaceans, for example, afford suitable 

 nourishment for the more advanced post-larval fishes, the 

 multitudes of larval crustaceans {Nauplii) are adapted to the 

 needs of the smallest larval food-fishes. Now this plant-life 

 is specially rich in April and May, just when the larval 

 and very young post-larval fishes appear more abundantly in 

 the inshore waters, so that the cycle is nearly complete, viz. 

 from the inorganic medium — through microscopic plant and 

 larval crustacean — to the post-larval fish. We have mentioned 

 the neighbourhood of an estuary as a prolific source of food for 

 young fishes, and we need only explain further by instancing the 

 ease of mussel-beds, which for months pour countless myriads 

 of larval mussels into the adjoining sea, far beyond the needs of 

 the area as regards mussel-culture, and which form a favourite 



' The fact that certain fishes feed on Infusoria has not been overlooked. 



