464 F. W. GAMBLE. 



Among the Macrorhynchus collected at Plymouth were two 

 species apparently new. Since^ however, my observations are 

 incomplete, I will not further describe them than by saying 

 that one species closely resembled M. mamertinus, v. Graif, 

 in the form and position of its gonads. The pharynx was not 

 so strongly developed. 



ii. Venenosi. 



24. Macrorhynchus heligolandicus, MetschnikoflF (37). 



Length "5 — 1*5 mm. Body rounded at both ends, 

 cylindrical, white, sometimes with brown spots. The pro- 

 boscis is typical but small. The bilobed brain bears 

 lenticulate eyes. The pharynx is rather small, placed as far 

 in front of the ceutre of the body as the genital pore is behind 

 it. The reproductive organs were first described by Jensen. 

 The great variability of certain (especially the chitinous) 

 parts, their complexity, and the presence or absence of certain 

 accessory organs (spermotheca, &c.) according to the particular 

 stage of development, render this perhaps the most difficult 

 of all Turbellaria to elucidate. Personally I have found 

 young specimens ("5 — 1 mm. in length) fairly intelligible. la 

 these the yolk- glands form finger-shaped masses extending 

 from the base of the pharynx to the genital pore. In the 

 adult they become reticular and very bulky. The elongate, 

 narrow germaria consist of a single row of ova for the 

 greater part of their length. Behind their point of union is 

 the large spermotheca. All these organs, the yolk- germ-glands 

 and spermotheca, open into a single female genital canal. This 

 canal is chitinised internally, and leads to the genital atrium. 

 For an account of the male gonads with figures see v. Graff, 

 'Monographic,' pp. 330-1, pi. ix; and Jensen, 'Turbellaria 

 Norvegise/ pi. iv. The most important fact is that in 

 addition to a chitinous sheath for the " granule-secretion," 

 there is a common one for both this and the terminal vas 

 deferens (see v. Graff, ' Monogr.,' p. 1G6, woodcut, fig. 9, G.). 

 The poison-organ consists of a hollow chitinous stylet 



