96 Ohio Naturalist. [Vol. 1, No. 6 



SPONGES AND BRYOZOANS OF SANDUSKY BAY. 



F. L. Landacre. 



The two small groups of fresh water sponges and Bryozoa re- 

 ceived some attention at the Lake laboratory during the summer 

 of 1900 



All our fresh water sponges belong to one family, the SpongiUidae, 

 which has about seven genera. They differ from the marine sponges 

 in two particulars. They form skeletons of silicon only, while 

 marine sponges may form silicious or limy or spongin skeletons. 

 The spongin skeleton is the one that gives the bath sponge its value^ 



They also form winter buds or statoblasts which carry the 

 sponge over the winter and reproduce it again in the spring. This 

 peculiar process was probably acquired on account of the changes in 

 temperature and in amount of moisture to which animals living in 

 fresh water streams are subjected. The sponge dies in the fall of 

 the year and its skeleton of silicious spines or spicules can be found 

 with no protoplasm. The character of the spines in the body of the 

 sponge and those surrounding the statoblast differ greatlj^ and those 

 around the statoblast are the main reliance in identifying sponges. 

 So that if a statoblast is found the sponge from which it came can 

 be determined, and on the other hand it is frequently very difficult 

 to determine the species of a sponge if it has not yet formed its stato- 

 blast. The statoblast is a globular or disc-shaped, nitroginous cell 

 with a chimney-like opening where the protoplasm escapes in the 

 spring. The adult sponge is non-sexual but the statoblasts give rise 

 to ova and spermatozoa which unite and produce a new sponge. The 

 statoblast is considered as the sexual generation. 



Three species belonging to one of the seven genera were posi- 

 tively identified. 



Spongilla fragilis, Leidy, a very common form was found on sub- 

 merged rocks on the south side of the bay near the city in great 

 abundance. Its yellow statoblasts are numerous and placed in 

 layers near the base of the sponge on the rock to which it is 

 attached. 



Another species Spongilla cinerea, Carter, was found on floating 

 timber. It is ashen gray in color. 



A third species Spongilla aspinosa, Potts, was found in Black 

 Channel and near the city on submerged rocks. Its color is green. 

 Other species were found but not definitely determined. 



The fresh water Polyozoa comprise a small group of animals- 

 resembling the sponges in the process of statoblast formation, but 

 otherwise totally different. Their real relationship is not definitely 



