DR. COBBOLD ON ANIMAL INDIVIDUALITY. 165 



latter to an individualized, free, constituent portion of tbe " bio- 

 tome." The propriety of this arrangement will, I think, appear 

 in the sequel. Let us, therefore, in the next place, glance at the 

 life-phases of one of the cestodes. Those of Tcenia serrata may 

 be tabulated thus : — 



ZooLOGiCAli INDIVIDTTAI {Taenia serrata). 



a. Ovum in all stages "] 



I. Six-hooked embryo, boring larva, or proseolex [-Primary "biotome." 



c. EestiQg larva, scolex, or Cysticercus pisiformis J 



d. Sexually immatxire tapeworm in all stages . . . i 



e. Mature tapeworm-colony, strobile, or Tcenia. . . V Secondary " biotome." 



f. Segment, free-joint, or proglottis (zooid) J 



According to Prof. Huxley's views, in the above "individual" 

 the stages a, h, c, d would collectively represent the first life-phase 

 or " protozooid," whilst the final phase,yj would be the " deutero- 

 zooid." I have, indeed, with Professor Huxley's approval, so re- 

 presented them in my introductory treatise on Entozoa ; but, 

 recently, I have not been able to satisfy myself that the nomen- 

 clature in question meets all the requirements of the case. In 

 my view, the six -hooked embryo is as much an individualized form 

 as the C^sticercus-stage, whilst the latter is as much a life-phase 

 as the proglottis itself. Why therefore may we not here recognize 

 three zooids (proto- deutero- trito-zooids), instead of two only, after 

 the manner suggested by Prof. Huxley ? If this view be accepted, 

 our Tcenia serrata, in its full zoological individuality, would be 

 represented by two biotomes, the primary one comprising two 

 individualized phases (the proseolex and scolex, or protozooid and 

 deuterozooid), and the secondary one comprising a practically in-, 

 definite number of individualized forms or tritozooids. In the one 

 case the independent life-phases are the result of metamorphosis, 

 but in the other they are the product of gemmation. Let us 

 next see how the matter stands in regard to one of the Trema- 

 todes, say, for example, the common liver-fluke (Fasciola Tiepatica), 

 which may be tabulated as follows : — 



> First " biotome." 



ZooioaiCAL INDIVIDTJAI (Fasciola hepatica). 



a. Ovum in all stages 



b. Ciliated free-swimming embryo 



c. Non-ciliated larva (nurse, germ-sac, sporocyst, "I i <c u' + '» 



reclia) J 



d. Active, migrating, tailed lai-va (eercaria) "i 



e. Encysted, resting larva (pupa) , > Third " biotome. " 



/. Sexually matm'e fluke (fasciola) J 



LINN. PEOO. — ZOOLOGY, VOL. VIII. 13 



