A Recent research onEpitokous Forms of Annelids. 1 



By Professor W. C. M'Intosh, M.D., F.E.S. 



Few subjects in comparatively recent years have excited more interest 

 than the remarkable changes which Prof. Ernst Ehlers of Gottingen 

 first pointed out in the Nereids at the reproductive period. The worms 

 in which these changes occurred were called by Ehlers epitokous forms, 

 while Prof. Edouard Claparede of Geneva termed them epigonous. 



Messrs. Maurice Caullery and Felix Mesnil, respectively of Lyons 

 and Paris, have described, in an important recent paper, the results of 

 their observations on a group hitherto unsuspected of harbouring such 

 features, viz., on the Cirratulidae, and more especially on the epitokous 

 phases of Dodecaceria concharum, Oerst., a species much more abundant 

 in the south than in the north, probably because the calcareous rocks 

 in which it bores are more characteristic of the French shores and those 

 of southern England, and the growths of Lithothamnion, into which it 

 likewise perforates, more luxuriant in these genial waters. 



Before entering on the special subject of the epigamy of the 

 Cirratulidae, it may conduce to perspicuity if we take a brief survey of the 

 groups in which these remarkable sexual phases are at present known. 

 No epitokous forms have hitherto been met with in the Amphinomiclae, 

 including, for the most part, somewhat sedentary annelids like 

 Euplirosyne and Spinther ; nor is it a prominent feature in the Aphro- 

 ditidae, the only types that can be mentioned in this connection being 

 Dreischia and Nectocliaeta, pelagic forms the life-history of which is 

 not yet sufficiently known to. warrant accurate deductions on the 

 subject. It is possible they are allied to such as Evarne hubrechti and 

 Evarne johnstoni, forms in which the bristles are much elongated and, in 

 certain examples, the eyes considerably enlarged. Like some other 

 groups of annelids, moreover, the young stages of the Polynoidae are 

 characterised by greatly elongated bristles during their pelagic life, but 

 no reliable deduction as to the connection with the epitokous condition 

 in the adult can be drawn from this feature. 



No example of epigamy is known in the Nephthydidae, yet at St. 

 Andrews a form of the common Ncphthys caeca, 0. Fabr., shows a 



1 Caullery and Mesnil, "Les formes epitoqiies et revolution des cirratulieus," 8vo, pp. 

 200, with 6 plates ; Paris, 1899, price frs. 7.50. 



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