4.60 Memoir Sears Foundation for Marine Research 



than the larger parent fishes.^" Males mature" at about 600 to 800 mm. and females at 700 

 to 1,000 mm. in different localities. Most of the adult males are from two feet to slightly 

 . less than three feet in length, the females from a little less than lYz feet to almost 3 V2 feet, 

 averaging about 7-1 pounds in weight; the maximum length attained is about four feet; 

 occasional very large fat females may weigh 1 5 pounds, and a weight of 20 pounds has 

 been reported. 



Developmental Stages. It has been known since Aristotle's day that the Spiny Dog 

 is ovoviviparous. The eggs are large, with much yolk. During the early stages of develop- 

 ment those in each oviduct, one to four or more in number, are enclosed in a thin, amber- 

 colored, horny capsule (known as a "candle") which tapers to a fine tip anteriorly but 

 to a blunter end posteriorly; this capsule later breaks down to leave the embryos free 

 in the oviduct. The young have no placental attachment to the uterine wall of the mother, 

 but the latter is complexly folded and has numerous highly vascular papillae. It has been 

 reported that the developing embryo gains about 40 per cent in weight over that of the 

 ripe egg, presumably by absorption of water through the yolk sac, or at least chiefly so.^' 

 While the embryos are developing, a fresh set of ovarian eggs are growing to take their 

 place. At Woods Hole the number of young in a litter is commonly four to six, sometimes 

 as many as eight to eleven, or as few as two. 



According to recent studies the period of gestation is about 1 8 to 22 months, whether 

 in the Black Sea,^^ the English ChanneF" or the western Atlantic."^ Accordingly, the adult 

 females taken in summer and autumn in the Gulf of Maine contain either very small em- 

 bryos that grow to an average length of about 17 mm. by September, or much larger ones 

 ranging from 7 to 1 1 inches by that month, i.e., nearly full term. 



Habits. Spiny Dogs are neither swift swimmers nor very active, putting up little 

 resistance when hooked. They may be either scattered or in schools, and in the latter case 

 it appears that they continue to stay together as they grow. As a rule a given school con- 

 sists either of small immatures of both sexes in almost equal numbers, of medium-sized 

 mature males and immature females, or of large mature females. It is common knowledge 

 that they are constantly on the move, their appearances and disappearances being so erratic 

 that where there may have been good fishing for cod one day there may be only Dogfish 

 the next, and nothing at all the day after, they having departed in pursuit of the better 

 fish they had driven away. They use their spines for defense, curling around in a bow to 

 strike, and it is probable that the spines are slightly poisonous, the general report to this 



:6. See Templeman (Res. Bull. Dep. Nat. Resources Newfoundland, 15, 1944: 44) for a detailed account of the 



life history of the Spiny Dog in Newfoundland waters. 

 27. Eng'lish Channel data. 

 i8. See Scammon and Minot (in Keibel, Noimaltafeln Entwick. Wirbelt., 12, 191 1) for excellent description and 



illustrations of embryonic development. For recent accounts of the uterine wall and of the gain in weight of 



the developing embryo, see Widakowitch (Z. wiss. Zool., SS, 1907: 499, pi. 30, 31), Ranzi (Pubb. Staz. zool. 



Napoli, 75 [3], 1934: 372) and Templeman (Res. Bull. Dep. Nat. Resources Newfoundland, 15, 1944: 45). 



29. Popovici, in Grig. Antipa. Homm. Ocuvre, Bucharest, 1938: 44S- 



30. Ford, J. Mar. bid. Ass. U. K., N. S. 12, 1921:481. 



31. Hisaw and Albert, Biol. Bull. Wood's Hole, 92 (3), 1947: 187. 



