354 mn c. eliot on xuDiBRAxcns [Dec. 1, 



The mode of origin of new organs is a morphological problem to 

 which little attention has been given, although it is of great 

 biological interest. The most obvious analogies with the present 

 case are svich changes of function and structure as the trans- 

 formation of the lower part of the pharynx into the thyroid gland 

 or the metamorphosis of part of a gill-slit into the middle 

 chamber of the ear; but I do not remember any case exactly 

 similar to the present whei-e the protoblastic structure, having 

 fulfilled its function, degenerates, but is replaced by a deutero- 

 blastic structure with a new function. It is interesting to notice 

 that the raw materials for this deuteroblastic growth occur in 

 many birds, inasmuch as the relic of the yolk-sac, or protoblast, 

 lingers throughout life, but it is only in a few cases that the relic 

 sprouts again and becomes the new organ. 



5. On some Nudibranchs from East Africa and Zanzibar. 

 Part III.* By Sir C. Eliot, K.C.M.G., H.M. Com- 

 missioner for the East Africa Protectorate, F.Z.S. — 

 Dorididse Crvptobranchiatse, I. 



[Received October 16, 1903.] 



(Plates XXXII.-XXXIV.t) 



This paper contains the results of an examination of a number 

 of Cryptobranchiate Dorids from Zanzibar and the East Coast 

 of Africa referable to Bergh's subfamilies Archidorididee, Disco- 

 doridida?, Diaululidse, Kentrodorididfe, and Platydoridida?. They 

 include the following s]Decies : — 



Archidoris Bergh. 



1. ,, africana, s.j). n. 



2. ,, mi?ior, sp. n. 



Sicmrodoris Bergh . 



3. ,, deypressa, sj). n. 



4. ,, ccdva, sp. n. 



Discodoris Bei-gh. 



5. . ,, hoholiensis Bergh. 



6. ,, ccendescens Bergh, variegata, subsi^. n. 

 Peltodoris Bergh. 



7. ,, angulata, sp. n. 



8. ,, cntrea., sp. n. 



Thordisa Bergh. 



9. „ villosa (A. & H.). 



10. ,, stellata, sp. n. 



11. ,, crosslandi, sp. n. 



* For Tart II. sec P, Z. S. 1903, vol. {. p. 250. 

 t Tor cxplfHiatioirol:' the Plates, see p. 385. 



