504. WALTER EDWARD COLLINGE. 
tate future investigations, obviating complications and mis- 
understandings that are sure to ensue from a disregard of some 
such system. 
1. The system of canals, branches, sense-organs, &c., I shall 
term the sensory canal system. 
2. The canal passing from the tail along the lateral portions 
of the trunk will be spoken of as the lateral canal—the 
term main canal is used in referring to the anterior portion 
of the lateral canal traversing the head. The various branches 
from the main canal which traverse the region of the head will 
be referred to respectively as the supra-orbital, the sub- 
orbital, and the opercula-mandibular or hyomandi- 
bular branches ; and the supra-occipital, the pre-orbital, 
and the ethmoidal commissures. Where a dorsal canal is 
present on the body it is spoken of as such. 
8. A system of fine dermal canals running from the main 
canal or a branch of the same, and opening by a series of fine 
branches to the surface by isolated pores, will be termed 
cluster pores (= peripheral organs of Allis). 
4, The fine pore-like openings spoken of as “ pin-hole” 
pores by many authors I shall term primitive pores, as 
illustrating the most generalised form, e. g. certain Elasmo- 
branchs and Polyodon, Psepherus, and Acipenser. 
5. Those canals which are unbranched and radiate from a 
given number of centres in the region of the head, having an 
expanded proximal end or ampulla, and opening to the surface 
by their distal end, and often spoken of as the canals of 
Lorenzini, I shall—following Ewart—refer to as ampullary 
canals. 
6. The series of organs known as smell-buds, sense-organs, 
pit-organs, Merkel’s buds, branchial sense-organs, &c., will be 
termed sensory organs. 
iv. FUNCTION. 
Of the function of this system but little is known. Lorenzini 
(50), 1678, was probably the first to regard it as a sensory one. 
Jacobson (88), 1813, stated its function more definitely; but, 
