346 Transactions. — Zoology. 



While speaking of the muscular tunic I referred to a tissue 

 ^Yhich occupied the proximal end of the anterior prolongation 

 of the body. This, in the specimens collected in winter, 

 presents a greenish colour, resembling that of the gonads ; this 

 colour in spirit, like the green of the gonads, changes to pink. 

 The tissue appears to be in connection with the anterior 

 gonads of both sides, especially that of the left, by the body- 

 wall. A section of the anterior prolongation shows that it is 

 full of blood-vessels, the tissue lying at the proximal end. 

 When examined microscopically it is seen that the tissue is 

 made up of small roundish bodies having exactly the struc- 

 ture, size, &c., of unripe ova. 



Histology of the Problematical Organs on the Intestine. 

 These structures are covered with the layer of ccelomic 

 epithelium covering the latter, so that they appear as outpush- 

 ings of the w^all of the intestine into the peribranchial cavity. 

 They are formed of connective tissue full of blood-spaces, 

 their structure, in fact, being simply that of the intestinal 

 wall. Through the blocks themselves, and in the wall of the 

 intestine below, wdnd very numerous tubules. These branch 

 free, and end in terminal dilatations or ampullse. Both tubules 

 and ampullae are Hned with a single layer of low cubical cells. 

 They appear to correspond to those described in Ascidia, 

 Perophora, &c., as ramifying over the stomach and part of 

 the intestine, the difference being that the organ in Boltcnia 

 ■IKichydcrmatina extends almost to the posterior end of the 

 body. 



The histological structure of the brain I have not been 

 able to make out at all satisfactorily. The nerve-cells are 

 small, and the nerve-fibres lie beneath. The neural gland I 

 could not discover at all, unless it corresponded to certain 

 tubules among the brain-tissue. These were small clear-walled 

 tubules, in connection with which appeared to be secondary 

 vessels with small ampulla. In the walls of some of these 

 vessels were what appeared to be concretions, on which acetic 

 acid (1 per cent.) had a slight effect. The cavities of the 

 dorsal tubercle are Hned by a layer of columnar epithelium 

 provided with very long cilia. Under the epithelium is a 

 layer of connective tissue continuous with that of the mantle. 



In concluding this paper I might take the opportunity of 

 drawing attention to the close resemblance Boltcnia michy- 

 dermatina bears to Culeolus in certain important points of 

 structure. In some of these points, as far as I can gather, it 

 differs from other genera of Boltcnia, and about other points I 

 am uncertain. The description of Culeolus is taken from 



