Dr. E,. GreefF on Autolytus prolifer. 177 



free offspring (Sacconereis and Polyhosti-ichus) and the primary 

 individuals of Autolytus. In his first memoir (Wiegmann's 

 Archiv, 1852) he not only correctly described the female Sac- 

 conereis, but also the male, indicating especially the charac- 

 teristic and different structure of the tentacles of the male. 

 He says (p. 70), " On the other hand, in the male, the two 

 lateral tentacles are fiircately divided into two diverging 

 branches, one of which is shorter than the other." In his 

 second communication (Miiller's Archiv, 1855, p. 489) he 

 definitely indicates the origin of Max Miiller's genus Sacco- 

 nereis from Autolytus. I have myself repeatedly observed 

 the whole of the forms just mentioned, and can confirm their 

 mutual relation in the most positive manner, although I 

 have made some divergent observations upon the mode of 

 proKfication. In his description of the structure of the 

 bud-sprouts {I. c. p. 74) Krohn says that, with the exception 

 of the first offspring at the hinder extremity of the parent 

 animal, produced at the expense of the hinder part of the 

 body of the mother (as, according to Leuckart and Frey, the 

 buds are produced only between the anterior and posterior 

 sections of the body, i. e. push themselves in between these), 

 and which is therefore a true product of fission, ova and 

 semen are not produced in any of the individuals subsequently 

 developed from buds, until at least the head with the traces of 

 the eyes and tentacles has been formed, I have had examples 

 under my eyes in which above the youngest sprout (which 

 therefore hung next to the parent animal) some segments of 

 the primary body already contained ova, although not the 

 smallest trace of head &c. could be detected either upon or 

 above these segments. In a case represented exactly in PI. VIII. 

 fig. 2, the hinder female sprout was already completely deve- 

 loped, with its head and three tentacles, and had its two fol- 

 lowing segments stuffed with ova, so that the second body- 

 segment had acquired an unusual degree of extension. But 

 the last segments of the primary animal impinging on the head 

 of the sprout also already contained ova, although no formation 

 of a head &c. could be detected. It is therefore evident that 

 the above statement of Krohn's cannot be maintained in its 

 universality. But our observation also imports a not unim- 

 portant modification into our notion of the mode of reproduc- 

 tion, as this case proves not only that the fully developed 

 sprouts are capable of producing ova &c., as has hitherto been 

 assumed with regard to Autolytus, but that ova may be pro- 

 duced even in the parent body (that is to say, in the nurse 

 itself), and, indeed, in segments which still belong to it entirely 

 and unchanged, as has already been ascertained in the case of 



