ARTTFICIAL PROPAGATION OF SHAD 



481 



the water into the jar, the other, eqiiall}" distant from the central 

 hole and the edge of the metal plate, admits the glass tube that 

 carries off the waste water. The central tube is connected by 3^-inch 

 rubber tubing with the petcock, which regulates the supply of water. 

 A groove in the inner surface of the metallic plate carries a rubber 

 collar, and when theplateisin place the tightening of the metallic screw 

 cap seals the opening hermetically. Both the inlet and outlet tubes 

 pass through stuffing boxes provided with gum washers and binding 

 screws. The central or feed tube is provided with stuffing boxes, 

 one on the top of the disk and one on the bottom, the better to hold 

 it to a true center. The outlet tube is provided with only one 

 stuffing box, and the binding ring is beveled. 



This type of jar works very satisfactorily with shad or other semi- 

 buoyant eggs. The outlet tube may easily be shoved down into the 

 jar, so that the dead eggs may be siphoned off. Its first cost is 

 about twice that of the open-top jars. The open-top jars may be 

 arranged in batteries or tiei"s, thus giving greater Jiatching and incu- 

 bating efficiency for the same floor space. The open-top jars are 



easier to set in place, and the breakage is 

 also less. The contour of the bottom of 

 the McDonald jar causes the dead eggs to 

 separate from the good eggs very readily. 

 Chase jar. — The Chase jar is similar to 

 the McDonald type in egg capacity. In 

 shape it differs at ihe bottom, neing more 

 pointed and having a solid base (lig. 7). 

 The main point of difference is at the top, 

 which, in the Chase jar, tapers in slightly 

 from its greatest diameter near the bot- 

 tom. The top is open and is fitted with 

 a metal band, from which extends a spout 

 about 3 inches long, 2 inches wdie, and % 

 inch deep. In operation the jar is placed 

 in such a position that the spout will dis- 

 charge directly into the fry tanks, thus de- 

 livering the overflow water with the fry 

 directly into the tank. Its egg capacity 

 is equal to that of the McDonald jar. 



All open-top jars cost less to purchase 

 than the closed-top type. The open jars 

 require slightly more water to operate 

 them successfully. The contour of the 

 bottom of the Chase iar is such that the eggs readily sesreffate, the 

 dead ones rismg to the top, where they may be removed. 



The other types of open-top jar, including the Do\\ming jar, are 

 similar to the Ciiase jar, with the exception of the metal band and 

 spout, which are not used, the glass being molded to foim the over- 

 flow channel. Another point of difference in jars of the McDonald 

 and Chase types is the contour of the bottom, which is so shaped as 

 to permit of an even regular motion of the eggs through the action 

 of the inflowing water. In the other types of open-top jars the shape 

 of the bottom is more pointed, making it extremely difficult to obtain 

 a uniform motion, so desirable and essential in the successful incuba- 

 tion of shad or similar eggs. 



Fig. 7,— Application of a measuring 

 scale to a jar of shad eggs 



