194 Mr. A. Hancock on the Anatomy of the 



sembling Cercarim. I have detected similar bodies in Bower- 

 bankia with large rounded heads and long tails ; they were very 

 numerous, and moved rapidly about in the interior of the cell in 

 the manner of tadpoles, that is, with a lateral undulating motion, 

 and are assuredly Spermatozoa. A testis may then be expected 

 to exist in the freshwater Bryozoa coextensively developed with 

 the ovary, and from analogy to be associated with it. It is not 

 unlikely therefore that these additional filaments from the stomach 

 may be really the male organ. 



Each polype does not appear to produce more than two or 

 three eggs ; in Plumatella Irequently only one. In P. Allmani 

 they, PL III. fig. 5/, are considerably depressed, of an oval form, 

 sometimes very long with the sides almost parallel ; they are very 

 large, being sometimes almost as wide as the diameter of the cell, 

 within which they are placed lengthwise ; the margins are reticu- 

 lated, yellow, pellucid, thin, and sharp, forming a well-defined rim 

 about the central portion, which is opake and black ; the covering- 

 is smooth, tough, and membranous. In Fredericella the egg is 

 broader and more regularly oval, of a brownish colour with the 

 margin narrow, plain and of a paler hue. The egg, PL IV. fig. 7 e, 

 of Paludicella, if egg it be, differs considerably from the above. 

 It is of an irregular oval shape, about half as wide as the cell, 

 colourless and pellucid ; the surface is marked with a few indi- 

 stinct, irregular, nucleated cells ; one larger and much more con- 

 spicuous than the rest, with a distinct round nucleus in the cen- 

 tre, is always to be seen on one side. The circumference of the 

 egg exhibits a double margin indicating an enveloping shield. 



The great size of the egg forbids the possibility of its escape 

 without the destruction of the polype*. In Plumatella, the 



* The polype of the marine species must also perish on the escape of the 

 gemmule. On examining some specimens of Bowerhankia in August, al- 

 most every cell was found to contain a large, round, opake, bright yellow 

 corpuscle. These corpuscles were for the most part in the lower portion of 

 the cells ; some however were halfway up, and others not far from the top : 

 those lowest down were the smallest, and as they approached the top they 

 increased in size until their diameter was nearly equal to that of the cell. 

 As long as the corpuscle remained near the lower extremity of the cell, the 

 polype was alive and active ; but was invaiiably dead when it had advanced 

 far upwards. At first the corpuscle does not appear to have any envelope, 

 but as it increases in size a distinct mai-gin makes its a})pearance, which 

 afterwards becoming wider and perfectly transparent, the corpuscle can 

 be seen rotating within by the aid of the long cilia that clothe its sur- 

 face. While watching one in this state under the microscope, I observed it 

 gradually elongate itself and pass with a glow ghding motion to the top of 

 the cell ; then forcing its way through the previously closed orifice, and 

 passing into the surrounding fluid, commenced to rotate with extraordinary 

 velocity : in an instant after this its enveloping membrane was torn open 

 and cast aside, and the little being, a broadly ovate gemmule, dashed at 

 once beyond the field of view. It at^terwards kept moving about in various 



