158 REPORT— 1888. 



3. The breadth of the metamer at the surface (lateral part). 



The amount of the overlap is given in some cases. Additional facts 

 of interest have also been given, as for instance : (a) the distinct 

 presence of a rectus ; (h) the separability of the dorsal part of the 

 dorso-lateral muscle mass ; and (c) the position of the limits with reference 

 to the metamers. The term rectus is used to indicate the median ventral 

 rauscles running from the anus (each side) along each side of the median 

 line to the pelvis, or from the pelvic to the pectoral girdle. 



The actual deviation from aline on the surface formed by a transverse 

 plane, is in many cases very considerable. The second metamer in Sargus 

 anmdaris gives a measurement for the outcrop of its dorsal portion of 

 17 mm., and this runs beyond the tenth part of the entire animal. The 

 metamer (dorsal piece) is directed from before backwards and downwards. 

 The dorsal part of the sixth metamer reaches 24 mm. and therefore tra- 

 verses one-sixth of the length of the fish. The thirteenth metamer gives 

 28 mm. for the first or dorsal piece. The entire length of the surface 

 line is nearly one half the length of the animal. 



Again the sixth metamer of Gohius capHo, which has a supero-inferior 

 diameter of 35 mm., is 67 mm. in length ; the length of the fish being 

 187 mm., and the number of metamers, 27. The twenty-third metamer 

 of the same fish gave a length of 52 mm. for a breadth of 20 mm. These 

 measurements take no account of the overlap. This overlap was 24 mm. 

 for the seventeenth metamer. 



The twenty-third metamer of ilugil cejjhalus reaches 11 mm. beneath 

 the antecedent metamers, and projects 5 mm. beneath the succeeding. In 

 some metamers I have noted 36 mm. as the range, and this means that for 

 an antero-posterior extent of 36 mm. an individual metamer by its zigzag 

 windings has a situation. The seventh metamer is 92 mm. long, whilst 

 the semi-circumference is 46 mm. The seventeenth is 72 mm. long, with 

 a sem.i-circumference of 29 ram. 



Trachinus Draco, one of Miiller's examples, shows 12 mm. for the 

 dorsal portion of the first, and 25 mm. for the twenty-fifth metamer. The 

 semi-diameter is 35 mm. in the first case and 18 mm. in the second. 



The dorsal part of the dorso-lateral mass is not easily distinguished as 

 a separate mass in all fishes. In Trigla I was able to separate it. In 

 Umbrina it can be separated for 10 metamers. 



In some fishes a distinct terminal bend is to be seen in the ventral 

 region as well as in the anterior part of the median line behind. In 

 Mustelus the bends are sharp. In various fishes, in Corvina, for example, 

 the dorsal curve is very distinct anteriorly. The dorsal bend is also seen 

 well in Belone, In Gohius the ventral and lateral. The rectus is seen in 

 Pagellus. Bands on each side of the anus run forwards to the pelvis. These 

 bands correspond to the bend inwards of the myotomes, and I am inclined 

 to think that there is some connection. The dorsal bend is well seen in 

 Uranoscopus scaber. 



Without giving any undue importance to the varieties in the ap- 

 pearances presented by the myotomes, I may state that between the 

 condition in which there are three sharp angles anteriorly and two pos- 

 teriorly superficial markings and that condition in which we have the myo- 

 tome running a direct course from the median dorsal line to the median 

 ventral, we have a great many varieties. How far the dorsal bends have a 

 connection with the separation of the dorsal fin muscles, the dorsal, &c., I 

 am not yet prepared to ofier any opinion whatever. The bend in the lateral 



