BRANCHLE OF TUNICATA. 283 



minae above the intestine and within the tubular cloak, to 

 which the water has access and egress by means of two 

 tubes placed at the posterior extremity of the body."* 



Let us, before proceeding, reflect a moment on that won- 

 derful diversity in the structure of the same organ here 

 exhibited to us in one class of animated beings : it is a fine 

 example, among many, of that variety in which the Creator 

 of all has seen good to indulge in the production of his 

 works, as if, to use the words of a favourite author, He 

 " willed to shew those whose delight it is to investigate his 

 works, by how many varying processes he can accomplish 

 the same end." f I see in it also a proof, that neither 

 external and physical circumstances, nor self-born desires, 

 have that great and almost creative influence in framing or 

 modifying animal structures which many imagine they have ; 

 for here are before us a crowd of animals whose soft bodies, 

 it will be allowed, are as susceptible of changes, or of being 

 moulded to one type, as any animals can be, and the uni- 

 formity of whose nervous system seems to prove that their 

 faculties and desires are much on a par ; yet, if we select 

 any large family from among them, we shall find them living 

 in the same seas, and in the same depths, and in the same 

 latitudes, and on the same food, and all breathing the same 

 air ; but, so far from showing a perfect agreement in their 

 exterior organs, on which these causes are said to operate 

 so efficiently, we find all is diverse, whether we look to the 

 position, the form, or the structure of the organs. These 

 are now, my friend, such as they were when the creatures 



* Comp. Anat. Trans, ii. 147. 



+ " Most of the Ascidise are coarse, unsightly, deformed-looking animals, 

 utterly void of that external symmetry and beauty, rendering many of the 

 tenants of the waters so interesting. Nor is it in this only, that they should 

 fail to attract the spectator's notice. They testify neither instinct, action, 

 nor motion, nor even the symptoms of life, farther than slight enlargement 

 and reduction of size, together with contraction and expansion of the two 

 tubular orifices of the body. No sensible alteration follows abstinence or 

 repletion ; the external form undergoes scarcely any modification from 

 health or disease ; even the lapse of time, that universal consumer, seems 

 hardly to make any impression on the shapeless mass, which is rooted im- 

 moveably from the first moment, on the same spot to vegetate, live, or die. 



" Such is the case, with but few exceptions, during any ordinary or rea- 

 sonable period, that may be occupied in observation. 



" Yet, let us recall what is disclosed when this rude object is stripped of 

 its external integuments, from which some of the germs may be withdrawn, 

 almost as from a bag. How complex the structure thus displayed ; what a 

 wonderful arrangement of muscular, respiratory, circulating, secretive, and 

 digestive organs, adapted for discharging the vital functions, all proving the 

 handiwork of the Great Architect, as directed towards a common end." SIR 

 J. G. DALYELL. 



