222 SUMMABY OP OUBKENT BESEABOHES EELATING TO 



embryo becomes free ; it is at first of tbe shape of a rounded, bottle 

 with a very short neck, but in a few days it has the form of a club 

 with a long handle; the point of attachment of the handle to the 

 body-wall represents the seat of origin of the primitive bud, and it is 

 just here that later on there is developed the common external orifice 

 of the genital apparatus (Helicid^e), or the opening of the female 

 ducts (Lymngeidse) ; the swollen part of the club-like organ is free, 

 and separates more and more from its point of attachment, in such a 

 way that the primitive bud soon becomes filiform, and has its superior 

 end hidden in the lobes of the liver ; this end forms, later on, the 

 site of the sexual elements. On the basal or peripheral part a 

 secondary bud — the penial bud — appears, and at the same time the 

 surface of the primitive bud presents a peripheral muscular differentia- 

 tion, the elements of which are all arranged along the long axis of the 

 bud ; a similar differentiation soon appears on the penial bud. Clefts 

 appear in the median part of the primitive bud ; one, which extends 

 towards the base and reaches the penial bud, has been called the 

 utero-deferent cleft, and it separates the two cords, one of whicli 

 becomes the oviduct and the other the efferent canal. Another 

 extends towards the apex, and, as it separates off the copulatory 

 pouch, it may be called the utero-copulatory cleft. Further pro- 

 liferations of the primitive bud give rise to the albuminiparous gland 

 and the diverticulum. The free tip then proliferates and begins to 

 give rise to the hermaphrodite gland. A fresh bud now appears on 

 the primitive one, which may be called the sagittal bud ; this will 

 ultimately form the dart sac. 



The observations of the author demonstrate the continuity of all 

 the parts of the genital apparatus from the first stages of development, 

 and utterly oppose the doctrine of fusion promulgated by Eisig ; the 

 genital apparatus of the Helicidas arises, as a whole, from a single 

 primitive outgrowth. 



The further development of the parts is described, and in conclusion 

 there is an account of the male and female products ; the ovules have 

 a degenerated and transitory follicle which goes to aid the store of 

 nutriment of the egg, and its elements arise from the perinuclear 

 protoplasm ; the male ovules give rise to proto- and then to deuto- 

 spermatoblasts, the latter forming each a packet of spermatozoa. 



Post-embryonic development of Najades.* — By infecting fishes 

 with the parasitic larvae of Anodonta, Herr F. Schmidt was able to 

 study the as yet but little known post -embryonic development of 

 these forms. 



In regard (I.) to the anatomical structure of the ripe embryo, Herr 

 Schmidt (a) corroborates the statement of Forel and Schierholz, 

 opposed by Eabl and Flemming, that the posterior end of the young 

 mussel is that at which the two lateral pits, the " Mittelschildtasche " 

 of Flemming, and the ciliated patch are situated, (b) Between the 

 two laterally placed pits lies the foot-pad, in front of this Flemming's 

 "Mittelschildtasche," and behind it the ciliated patch. In cross 



* Arch. f. Naturgesch., li. (1885) pp. 201-34 (2 pis.). 



