108 Proceedimjs of the Royal Society of Victoria. 



(J. The Lateral Orr/ans. 



By way of preface to tliis ]iortion of our subject, I will 

 take the liberty of quoting part of Pi'ofessor Hubrecht's 

 concise and excellent account of the lateral organs given 

 in his ai'ticle on Nemertines in the latest edition of the 

 Encyclo-pcedia Brito.nnica : — 



"This apparatus is usually known under the name of the 

 " lateral organs. To it belong [a) superficial grooves or 

 " deeper slits situated on the integument near the tip of the 

 " head, {b) nerve lobes in immediate connection wdth the 

 "nervous tissue of the brain, and (c) ciliated ducts penetrat- 

 "ing into the latter and communicating with the former. 

 " Embryology shews that originally tliese different parts are 

 "separately started, and only ultimately become united into 

 "one. Two lateral outgrowths of the foremost portion of 

 " the oesophagus, afterwards becoming constricted off, as 

 " well as two ingrowths from the epiblast, contribute 

 "towards its formation, at least as far as l>oth Hoplo- and 

 " Schizonemertines are concerned. . . These posterior 



"brain-lobes, which in all Schizonemertines are in direct 

 " continuity of tissue with the up|)ei' pair of ])rincipal lobes, 

 " cease to have this intimate connexion in the Hoploiuinertea ; 

 " and, although still constituted of (1) a ciliated duct, opening 

 "out externally, (2) nervous tissue surrounding it, and 

 " (3) histological elements derived from the oesophageal 

 " outgrowths, they are nevertheless here no longer constantly 

 " .situated behind the upper brain lobes and directly 

 "connected with them, but are found sometimes behind, 

 " .sometimes beside, and sometimes before the biuin-lobes. 

 " Furthermore, they are here severed from the principal 

 "lobes and connected with them by one or more rather thick 

 "strings of nerve-fibres. In some cases, esi)ecially when the 

 "lobes lie before the brain, their distance from it, as well as 

 " the length of these nervous connexions, has considerably 

 " increased. . . . With the significance of these parts we 

 " are still insufficiently acquainted. . . . Wliether in the 

 " Hoplonemertines, whei'e the blood fluid is often provided 

 " with hfemoglobiniferous disks, the chief functions of the 

 " side organs may not rathei be a sensory one must be 

 " further investigated." 



This I take to be a fair summary of our knowledge of the 

 lateral organs- up to the present time, and 1 will now 



* For further details as to the marine forms the reader is referred to Biirgca-'s 

 fcxcellent memoir already referred to. 



