XXI 



OBSERVATIONS ON THE EXISTENCE OF CELLULOSE 

 IN THE TUNIC OF ASCIDIANS 



Quarterly Jou7-nal of Microscopical Science^ i. 1853 



A CAREFUL examination of a number of species of the Ascidian 

 genera Boltenia, Cynthia, Molgula, Phallusia, Syntethys, Aplidium, 

 Pyrosonia, and Salpa — including, therefore, every modification of the 

 type, has led me to the following conclusions with regard to the 

 structure of the mantle. The investigation was made with a full 

 knowledge of what had been done by Lowig and Kolliker and by 

 Schacht and I have only ventured to differ from them upon strong 

 evidence. 



I. In the most gelatinous forms of the test, as in Syntethys and 

 Salpa, it consists of a soft homogeneous or delicately-striated basis, 

 through which round nucleated cells (nuclei of Kolliker and Lowig) 

 are scattered. These cells present no ramifications, and the presence 

 of cellulose is demonstrated with very considerable difficulty. When 

 the iodine solution is added, the whole mass becomes coloured 

 yellowish-brown, the nucleated cells taking rather a deeper tint than 

 the rest. The addition of sulphuric acid slightly contracts the whole 

 substance, and if used with care, gives the edges the characteristic 

 blue tinge. The cellulose is evidently diffused through the inter- 

 cellular nitrogenous basis ; for the first evidence of the operation of the 

 sulphuric acid is seen in a slight diffused, even green shade, which is 

 produced by the incipient blue reaction of the cellulose mingling with 

 the existing yellow-brown colour. As the action of the test goes on, 

 the edges of the membrane become deep blue, while the green tinge 

 passes insensibly into the blue on the one side and into the yellow on 

 the other. 



As Schacht justly points out then, the substance of the test is not 

 pure cellulose but cellulose deposited in a nitrogenous membrane. It 



