280 



The internal duct is a small tube, smaller than the external duct, 

 and rises from the extreme posterior end of the gland. It runs for- 

 ward, closely adherent to the ventral side of the gland, to its anterior 

 end. where the duct opens into the body cavity. Its anterior portion 

 is expanded into the form of an elongated funnel, and is ciliated on 

 the interior (?). The cells lining the gland and ducts, are exactly 

 similar to those described by Ha swell 4 , for some australian species. 



The outside of the gland is covered by a layer of peritoneum con- 

 tinuous with that lining the interior of the hypoderm of the first 

 segment. 



Sexual Products. 



The ovaries are small rounded bodies, one on either side in each 

 segment behind the middle of the body, close against the dissepiment 

 separating that segment from the one in front of it. The ova lie loose 

 in the body cavity, completely filling it toward the posterior end. 



The external openings for the sexual bodies are in the posterior 

 part of each segment, opposite the ovaries. They are small round 

 openings, surrounded by a thin lip, which is made up of the three 

 body layers, hypoderm, muscles, and peritoneum, greatly reduced in 

 thickness, and containing also a special layer of circular muscles, 

 surrounding the opening. The arrangement of the parts is such that 

 a contraction of the body muscles would open, and a contraction of 

 these circular muscles would close, this opening. 



All of the specimens examined proved to be female ; hence further 

 study will be necessary to determine the structure of the male sexual 

 organs. 



5. Zur Entwicklung von Paludina vivipara. 



(Vorläufige Mittheilung.) 

 Von Dr. R. v. Erlanger aus dem Zoologischen Institut zu Heidelberg. 



IL Theil. 



eingeg. 3. Juni 1891. 



Im Besitz eines reichen Materials, sowie einer großen Anzahl von 

 Praeparaten und Schnittserien , habe ich es für zweckmäßig gehalten, 

 die bisher nicht berücksichtigten Puncte in der Entwicklungsge- 

 schichte von Paludina eingehender zu studieren. 



Ich beabsichtige im Folgenden die Entwicklung der Sinnesorgane, 

 des Gefäßsystems und des Geschlcchtsapparates kurz zu besprechen. 



4 Marine Annelids of order Serpulae.« Proe. Linn. Soc. N. S. Wales. Vul. IX. 

 p. 649. 1884. 



