BRANCin.K OK TUNICATA. 28.S 



iniiiii' above the intestine and within the tubnhir cU)ak, to 

 vvliic'li the water lias access and egress by means of two 

 tubes pUiced 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-horn desires, 

 have that great aiul 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 hodies, 

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

 moukled 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 And them living 

 in the same seas, and in the sanve de])ths, and in the same 

 latitudes, and on tlie same food, and all breatliing the. same 

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

 exterior organs, on which these causes are said to operate 

 so efliciently, we And 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. Aimt. Trans, ii. 147. 



+ " Most of the Ascidite are coarse, unsightly, deformcd-looking animals, 

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

 tenants of the waters so interesting. Nor is it in tiiis oidy, 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 re(hiction of siy.e, together with contraction ami expansion of the two 

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

 repletion ; the external form tmdcrgoes scarcely any modification from 

 healtii or disease ; even the la])se of time, tliat universal consiuner, seems 

 hardly to miike any impression on the siiapeless mass, wliich is rooted im- 

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



"Such is tlie 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 tliis rude olijcet is strip]icil of 

 its external integumentH, from which some of the germs may be witiidrawn, 

 almost as from a bag. How conij)Iex the structure tlius displayed ; what a 

 wonderful arrangement of muscular, resjiiratory, circulaling, secretive, and 

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

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

 J, G. Dalykij,. 



