THE PINEAL BODY 113 



LOPHOBRANCHII 



32. Syngnathus acus. Studnicka ('96). 386 The pineal organ 

 in this species is rudimentary, only the proximal portion of it 

 being present. In this there is a small lumen. 



33. Hippocampus spinosus. Studnicka ('96). 386 The pineal 

 organ in this form is a small, short sprout, the distal end of which 

 does not reach the roof. 



In all, thirty-three species of teleosts have been investigated. 

 Of these, thirty species present a more or less well-developed 

 pineal organ. In one form it is almost entirely absent present- 

 ing itself only as an inconspicuous rudiment. This is the case 

 in Syngnathus acus. In a second instance, Hippocampus 

 spinosus, the pineal organ is little more than a short sprout. In 

 five instances among the teleosts both pineal and parapineal 

 organs appear, the latter occurring either in the adult, which 

 is rare, or during the earlier stages of development. Both 

 organs appear in the anlagen in Coregonus albus, Lucioperca 

 vitrea, and Catostomus teres, but later disappear in these forms. 

 Both organs are well marked in anlagen and remain as discern- 

 ible rudiments in Salmo purpuratus and fario and also in Argyro- 

 pelecus hemigymnus. In one instance, Leuciscus cephalus, 

 there was definite evidence of secretory activity in the pineal 

 organ. In three species there was evidence of a retina in the 

 pineal organ, either because of the presence of specialized sensory 

 cells or of nerve fibers coming into connection with these cells. 

 In three instances there was a distinct parietal foramen. It is 

 significant in this connection to note that in no instance in 

 which there was a retinal-like structure or cellular formation 

 and arrangement suggestive of a retina, did there occur a parietal 

 foramen. In seven cases the end- vesicle of the pineal organ was 

 lodged in a fossa on the under surface of the skull. In seven 

 species, namely, Cobilis fossilis and barbatula, Lophius pisca- 

 torius, Cyprinus carpio, Carassius auratus, Anarrhichas lupus, 

 Pleuronectes platessa, and Clupea harengus, there is evidence 

 of a nervus pinealis or a tractus pinealis. All of these descrip- 

 tions except one are given by Studnicka. 386 This observer makes 

 the statement that there is no nervus pinealis in Ophidium 

 barbatum. 



MEMOIR NO. 9 



