Report of the State Geologist. 



531 



brachiopod possesses any organs of special sense, but in the 

 embryos of several genera, bodies believed to perform such func- 

 tions have been observed. 



Brooks has shown the existence of an auditory organ in Lingula, 

 similar to that of the lamellibranchs, viz. : a pair of otocysts con- 

 taining vibratile otoliths, which are situated close to the nerve 

 collar. 



Similar structures were observed in Dhcinis* \ by Muller. 

 The very young of Thecidium, Cistklla. and Discinisca bear two or 

 four minute pigment spots on the cephalic segment, which are 

 believed to be organs of vision. All trace of these sense organs 

 is resorbed in later growth. 



The Reproductive System. 



It has already been observed that the brachiopods, so far as 

 known, not only reproduce by ova, but are also dioecious. It is 



Fio. 190.— Oviduct of Hemithyris psittacea, 

 a, laminated portion; 6, tubular portion; 

 c, wrinkles of lining membrane; d, external 

 opening; e, vescicle; /, g, blood-vessels. 

 (Hancock.) 



Fig. 191.— Fragment of ovary 

 of Crania. (Joubin.) 



difficult, however, to distinguish the male from the female animal, 

 except upon the approach of fecundity. Then the testes become 

 enlarged by the colorless spermatic fluid, and take on a pale hue ; 

 on the other hand, as the ovaries of the female become crowded 



83 



