NO. 1788. 



NORTH AMERICAN ERGASILID^— WILSON. 



299 



The ovaries are small egg-shaped bodies situated on either side of 

 the anterior portion of the dorsal surface of the stomach. Each con- 

 sists of a mass of small nucleated cells, the ova, which are formed by 

 karioldnetic division at the posterior, free end of the ovary, and grad- 

 ually pass out into the oviduct which is 

 o;iven off at the wider anterior end. The 

 body of the ovum accumulates yolk granules 

 and increases greatly in size as it passes into 

 the oviduct. The latter seems to be an out- 

 growth from the ovary as in free-swimming 

 forms. At first it is a simple tube without 

 convolutions, extending backward to the 

 genital segment. 



But as the ova issue into it out of the 

 ovary it rapidly sends out uterine processes 

 backward and forward and laterally until 

 in fully mature specimens it fills the entire fiq. is.— dorsal mew of cara- 



1 1 ,• p ,1 •,! PACE OF EeGASILUS CENTRARCHI- 



dorsal portion of the carapace with a mass ^^^^ ^^^^^^ ^.,^3^^^^^ ^^ 

 of opaque white ova tightly packed to- first two egg cells that issue 

 getlier. The gradual growth of these uter- 

 ine processes is well shown in the series of figures (18 to 24) here- 

 with presented. 



At first a single large ovum appears in either oviduct just behind 

 the suture which marks the division between the head and first 

 thorax segment, and some little distance from the mid-line (fig. 18). 



These ova then extend backward throughi 

 the first thorax segment to its posteriorj 

 margin (fig. 19). They next accumu- 

 late at the point where they first ap- 

 peared and push forward into the head, 

 approaching each other on either side 

 of the mid-line (fig. 20). Again accumu- 

 lating at the same point, each oviduct 

 sends out a lateral process which ex- 

 tends obliquely forward and downward 

 toward the base of the second antenna 

 (fig. 21). The entire portion within the 

 first thorax segment now thickens, ap- 

 proaching close to the mid-line, and 

 another lateral process is sent out in 

 the posterior portion of the segment and 

 nearly at right angles to the body axis. This process also curves 

 over ventrally and eventually approaches close to the ventral wall 

 of the body (fig. 24). Each of these processes thickens laterally as 

 well as increases in length (fig. 22), until eventually the space in the 



Fig. 19.— The first uterine processes 



FORMING posteriorly THROUGH THE 

 FIRST THORAX SEGMENT. 



