4 Laidlaw, Polydad Turbellaria in the British Museuin. 



•" Godthal. Mr. Holboll's collection. 60 faths."- One 

 specimen. 



The external features and as much of the anatomy as 

 could be determined from the inspection of a specimen 

 cleared in cedar oil agreed closely with the specimen so 

 beautifully figured by Jensen ['78]. I cut serial sections 

 through the genital tract ; these have revealed the follow- 

 ing points of interest. The prostate gland is divided up 

 longitudinally into about twelve chambers. The vagina 

 is not developed into a bursa copulatrix, and the accessory 

 parts are without muscular walls. These accessory parts 

 consist of a duct, which Jensen described as having a 

 curious moniliform appearance ; the accessory duct, and a 

 large accessory vesicle. The cells lining the duct form 

 here and there little glandular ' bunches ' or clusters of 

 cells on either side of the duct, which in their neighbour- 

 hood has its lumen much contracted. It is no doubt their 

 presence which gives the accessory duct its moniliform 

 appearance. The walls of the accessory duct are but 

 poorly furnished with muscle fibres. The ' bunches ' con- 

 sist of small pear-shaped darkly staining cells, with rather 

 large nuclei. The smaller ends of these cells project into 

 the lumen of the duct. 



The accessory vesicle is also only feebly muscular, it 

 is lined with columnar secreting cells, which recall in 

 appearance to some extent those of the receptaculum 

 seminis of P araplanocera. The shell glands lie about the 

 accessory vesicle. 



It is evident, I think, that this species is closely 

 related to Leptoplana nationalis described by Plehn 

 ['96]. I am not able to determine whether the relative 

 extent of the main-gut is the same in the two species as 

 the specimen of L. droebachensis at my disposal is very 

 much contorted. Plehn's specimen however differs 



