420 " THETIS " SCIENTIFIC RESULTS. 



When, therefore, it was found that the "Thetis" material did 

 not allow of a complete investigation, the Curator decided that I 

 should examine the Gulf specimen, and see if it was possible to 

 recover therefrom the details lost from the primary source. The 

 double investigation was rewarded with even better results than 

 we had expected. 



The two species prove to belong to one genus, and from the 

 second most of the details lost in the tirst were recovered. 



The following is a concise summary of the results obtained 

 from each investigation, in the order in which they are treated 

 in the following pages. 



Megalatractus aruanus, Linn. : — 



(1) External features generally and the organs of the pallial 



complex are described. 



(2) Digestive system. The alimentary canal itself was dissected 



out and is described ; its position and relation to the other 

 organs are noted, except as regards the anterior end of the 

 oesophageal loop and the nerve-ring. 



(3) Nephridiiim. Its shape and macroscopic appearance 



generally are described. 



(4) Vascular system,. All the principal vessels and sinuses are 

 described, and the circulation of the blood discussed. 



(5) Nervous systevi not known. 



(6) Reproductive systerti. The specimen was a female ; only 



the ovary and uterus are described. 



SiPHONALiA maxima, Tryon : — 



(1) External features and organs of the paUial complex. 



(2) Digestive system. Particular attention was paid to the 



anterior portion of the S3^stem ; the relation to the nerve- 

 ring, the oesophageal and salivai'y glands, are described. 



(3) Nephridiuin practically unknown. 



(4) Yascidar system. The only particulars gleaned relate to 

 the heart and aorto-cephalica. 



(5) Nervous system. All the ganglia and their relations inter 



se are described, except the visceral ganglia. 



(6) Reproductive systems. Nothing is added to the account of 



the female complex given under the last species, but the 

 male complex is described in its entiret}'. 



(7) .4 section through the j^rohoscis. 



Throughout the two investigations, when the same oi'gan or 

 portion of an organ was obtained in both, it Avas found to be 

 essentially similar, the differences being of minor importance and 

 such as may well be regarded as specific. It has, therefore, as 



