254 Proceedings of the Royal Physical Society. 



Clutch of four eggs, taken 22d October 1879, from a nest 

 in the campo of Tala. 



Another clutch of four eggs, taken 23d October 1879, from 

 a similar nest. 



These average If^ x l\l inch in size, and are identical in 

 shape and appearance with those of the lapwing. The nest, 

 also, exactly resembles that of the same bird, consisting 

 merely of a shallow cavity, formed by the bird's body, and 

 lined with a few straws. They have two, and sometimes 

 three broods in the season. 



XIV. On the "Olfactory Tubercle" as a Specific Character in 

 Sim]jle Ascidians. By W. A. Herdman, Esq., D.Sc, 

 F.L.S., Demonstrator of Zoology in the University of 

 Edinburgh. 



(Read 20tli April 1881.) 



Savigny appears to have been the first writer on Ascidians 

 who mentions the '' olfactory tubercle." * In his celebrated 

 " Memoires sur les Animaux sans Vertebres," he figures and 

 describes (under the name of " tubercule anterieur") this 

 curious organ in many different species. Since that time its 

 structure has been investigated more or less fully, and its 

 function discussed by nearly every ^vriter on the Tunicata. 



The organ lies at the anterior end of the branchial sac on 

 its dorsal edge, generally in close relation to the nerve gang- 

 lion. It is posterior to the circlet of tentacles, from which it 

 is separated by the smooth area called by Kupffer the " zona 

 pr^branchialis." This zona prsebranchialis on the two 

 sides is bounded posteriorly by the right and left peri- 

 pharyngeal bands, which, as they approach the dorsal region, 

 bend posteriorly for a short distance so as to enclose a 

 wedge-shaped space before they unite at the anterior ex- 

 tremity of the dorsal lamina. This space, in which the 



* Julin's recent investigations {see Archives de Biologie, t. ii., fasc. 1) have 

 thrown grave doubts on the supposed sensory function of this organ. I still 

 call it the "olfactory tubercle," as that is the name under which it is best 

 known in this country, but do not mean thereby to express any opinion on its 

 nature as a sense organ. 



