858 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



(opposite the anus) being larger than the others. Five pairs occur behind the yolk-sac, 

 while a sixth exists in front of its posterior border. These organs are not opposite each 

 other, but the left is a little in advance of the right. The marginal fin is not deep, and 

 extends a short distance on the yolk. Very fine cells are visible on its surface. 



The young fishes are somewhat delicate in confinement, the oldest example reared 

 in the laboratory being represented in Plate II. fig. 13a — about nine or ten days after 

 hatching. The yolk-sac has now shrunk considerably, and the snout projects forward as 

 a blunt process. The surface of the yolk-sac anteriorly in one example is minutely 

 papillose, but this is probably an abnormality. The pectoral fin is well developed, and 

 the eye is slightly silvery. The mere change of these young fishes from a deeper to a 

 shallower vessel suffices to cause distress, with speedy opacity and death. 



Ammodytes tobianus, L. — Young sand-eels were found during the Trawling Expedi- 

 tions in great numbers about the middle of April,* and they are similarly met with 

 annually in St Andrews Bay, generally at a depth of 4 fathoms. 



The youngest form associated with the sand-eel was procured in the mid- water net on 

 the 29th March, and measured 6 or 7 mm. in length. The body is slender and elongated, 

 while the head is large and bluntly rounded in front. The mandible projects considerably 

 beyond the premaxillary region when the mouth is widely open. The pigment of the 

 eyes (in spirit) is black, and scarcely a trace of the silvery sheen is noticeable. The eyes 

 closely abut on the front margin of the snout. The notochord passes straight backward 

 in the centre of the tail, which has only the fine and symmetrically arranged embryonic 

 fin-rays. The delicate marginal fin had been injured, and only a remnant existed in front 

 dorsally. The pectorals are largely developed. The anus opens about the end of the 

 middle third of the body. Black pigment-specks are distributed along the ventral 

 surface, viz., a single line from the pectorals a short distance backward, then a double 

 line (on each side of the gut) to the anus. Behind the latter a very closely dotted line 

 extends to the base of the tail. 



A large number of larval forms similar to the foregoing, though somewhat longer 

 (9 to 11 mm.), abounded in St Andrews Bay about the beginning of April, but their 

 identity is at present uncertain. 



What appears to be the next older stage (between 8 and 9 mm.) was captured on the 

 14th April. The marginal fin (which occurs all round) shows no differentiation, but the 

 increase of the hypural elements and the true fin-rays inferiorly cause a slight upward 

 bend of the tip of the notochord. A single dotted line of pigment passes from the 

 pectorals to the tip of the tail, and a series of large pigment-corpuscles exists on each side 

 of the alimentary canal in the middle third. The eyes now show a slightly silvery sheen. 

 The mandible is still prominent. Cartilaginous rays occur in those parts of the dorsal and 

 anal fins behind the vent. The pectorals are very large, much larger proportionally 



* Mobius and Heincke give the spawning season of A. lanceolatus, according to Bloch, in May, and mention that 

 Malm found a female with enlarged ova in June. A. tobianus, again, is said to spawn in summer (i.e., from May to 

 August). 



