SMALLWOOD. — POLYCERELLA ZOOBOTRYON. 623 



tate gland. A short distance before the formation of the ampulla, the 

 hermaphroditic duct receives the duct from the mucous gland. 



2. The prostate (Figure 8) duct is relatively short, only 100 micra 

 long, and its walls are 20 micra thick. As it emerges from the pros- 

 tate gland it turns ventrally and anteriorly to open without further 

 change of course into the genital atrium. 



3. The receptaculum seminis (Figure 8, rep. sem.) is an elongated 

 sac 85 micra long, 50 micra wide, and 25 micra thick, located on the 

 right side dorsal to the prostate gland and ventral to the kidney cham- 

 ber. The duct from the receptaculum seminis is 25 micra long and 8 

 micra thick ; it opens into the prostate duct as shown in Figure 8. In 

 copulation, then, the penis enters the prostate duct, which makes it 

 appropriate to designate this duct as the vagina. 



4. The oviduct opens with the prostate duct into the genital atrium. 

 From its origin it passes dorsally and to the left until the left side of 

 the body is reached. There it turns anteriorly and then crosses to 

 the right side, this time over the suctorial bulb, finally terminating in 

 the genital atrium. The oviduct (Figure 8, o'dt.) is divided into three 

 regions : (1) a terminal, thick-walled, muscular portion 45 micra wide, 

 extending from the prostate duct to the middle region ; (2) this is short 

 but much wider, being 60 micra in diameter, and thin walled ; it lies 

 over the suctorial bulb ; finally (3), the initial part is for 50 micra of 

 its length not more than 30 micra wide. The large cavity in the mid- 

 dle region of the oviduct contains a considerable amount of detritus ; 

 the only structures that could be identified were parts of the polyzoan, 

 upon which this species feeds. This region would seem to be, there- 

 fore, similar to a spermatheca, although placed in the oviduct. The 

 duct from the albumen gland opens into the oviduct in the last third 

 of its course, about 20 micra from the genital atrium. 



5. Penis and vas deferens. A fleshy triangular valve separates the 

 opening of the penis sac from the prostate duct and oviduct. The peni? 

 sac, 30 micra wide, may run crosswise in front of the anterior genital 

 mass or back close to the body wall and lateral to the anterior genital 

 mass (Figure 3). The penis has a general width of 10 micra, its end 

 becomes expanded into a head 12 micra wide. The duct running 

 throughout the center of the penis is 4 micra wide and heavily ciliated. 

 Bergh ('92, p. 149) states that the penis of Polycerella is armed with 

 hooks. Verrill ('80, p. 387), in describing P. emertonii, makes no men- 

 tion of the reproductive organs. Balch ('99, p. 151) says, "No arma- 

 ture of the penis could be made out in sections, but this was perhaps 

 owing to poor preservation." The enlarged end of the penis in P. zoo- 

 botryon is unquestionably ciliated and in specimens fixed in four dif- 



