212 ARTHUB B. SHIPLEY. 



fifth divides into two parts, the ophthalmic and mandibular ; 

 these have a common root. 



The seventh nerve at its first appearance supplies the first 

 or spiracular gill-cleft ; when this is converted into the ciliated 

 ring it continues to be supplied by the seventh nerve. 



The connection between the fifth, seventh, and tenth nerve 

 ganglia does not exist and must be of later origin. 



The tenth nerve has a large ganglion on its root and bears a 

 ganglion above each of the last six gill-clefts. No trace of the 

 ramus lateralis is to be seen. 



The origin of the ganglia on the cranial nerves has no 

 relation to the sense-organs of the skin ; these have not 

 appeared even in my oldest larva. 



Literature Referred to. 



(1) 1836. JoH. MuLLEB. — ' Vergleichende Anatomic der Myxinoiden, der 



Cyclostomeu mit durchbohrten Gaumen,' Berlin. 



(2) 1851. Stannitjs. — "Ueber den Bau den Muskeln bei Petroniyzon 



fluviatilis," ' Gottinger Naclirichten/ 1851. 



(3) 1856. Aug. Muller. — " Ueber der Eutwicklung der Keunaugen," 



' Midler's Archiv/ 1856. 



(4) 1856. Max ScHULTZ. — 'Die Entwickelungsgeschichte von Petromy- 



zon Planeri,' Haarlem. 



(5) 1864. Aug. Mtjllee. — " Beobachtungen iiber die Befruchtungserschein- 



ungen im Ei der Neunaugen," ' Verhandl. d. Konigsberger 

 Phys.-okonom. Gesellscb.' 



(6) 1867. Geenachek. — " Beitrage zur Erkenntniss der Muskeln der Cyclo- 



stomen und Leptocardier," ' Zeit. f. wiss. Zool.,' Bd. xvii. 



(7) 1870. OwsJANNiKOW. — 'The Development of Petromyzon fluvia- 



tilis ' (Russian). 



(8) 1873. Paul Langeehans. — " Untersuchungen iiber Petromyzon 



Planeri," Freilung, i B., 1873. 



(9) 1873. WiLH. MtJLLEK.— " Ueber die Hypobranchialrinne der Tunika- 



ten und deren Vorliandsein bei Aniphioxus und den Cyclo- 

 stomen," 'Jen. Zeit. f. Med. u. Naturwiss./ Bd. vii. 

 0) 1875. WiLH. MuLLEK.— " Ueber das Urogenitalsystem des Amphioxus 

 und der Cyklostomen," ' Jen. Zeit. f. Med. u. Naturwiss.,' Bd. ix. 



