TYPE PLATYHELMINTHES. 



139 



ce-jL_ 



ov 



in the Triclads otocysts are wanting, nor have ciliated lateral 

 depressions been described as occurring in the order. 



Little is known concerning the 

 excretory system. The reproduc- 

 tive system differs from that of 

 the other orders in that the male 

 and the female apparatus each 

 possess a separate opening ( $ and 

 ? ), there being no genital atrium 

 common to both. Both apertures 

 lie behind the mouth-opening, near 

 the posterior end of the body, 

 the male apparatus opening an- 

 teriorly to the female. The former 

 is similar in structure to what has 

 been described for the Triclads. 

 The female apparatus possesses 

 no vitellariurn, and the ovaries (ov) 

 are very numerous, lying in the 

 lateral parts of the body, their 

 various ducts uniting to form wide 

 canals which serve as uteri (ut). 

 These open into a single tube, the 

 vagina, which receives the secretion 

 of the numerous glands (sg) which 

 form the shell-gland 



In some forms there is situated 

 about the middle of the ventral 

 surface of the body a muscular 

 sucker which serves as an organ of 

 adhesion. Since the presence or 

 absence of this organ is in either 

 case associated with the occurrence 

 of other important structural pecu- 

 liarities, the order has been divided 

 into two suborders the C'otylea, 

 provided with a sucker (Thysano- 

 zoon, Eurylepta), and the Acotylea, in which it is absent 

 (Planocera, Leptoplanci). 



FIG. 74. A POLYCLAD TUKBEL- 

 LAEIAN, Leptoplaiia alcinvi 

 (.after LANG). 



ag = accessory gland. 



ce = cerebral ganglion. 



ov = ovary. 

 ph -- pharynx. 



sg = shell-gland. 



te = testis. 



ut = uterus. 



vd = vas deferens. 



vs = vesicula seminalis. 

 |,2 = male and female orifices. 



