2 BULLETIN OF THE 



tory at Wood's Holl, Mass., during the summer of 1889, and while at 

 Mr Agassiz's Newport Laboratory during the summer of 1890. To my 

 instructor. Dr. E. L. Mark, for many valuable suggestions during the 

 progress of my work and the writing of this paper, to Mr. Alexander 

 Agassiz, for the kind hospitality accorded me at his Newport Laboratory} 

 and to Hon. Marshall McDonald, United States Commissioner of Fish 

 and Fisheries, and Dr. H. V. Wilson, Assistant at Wood's Holl, for fa- 

 vors shown me while at the Wood's Holl Laboratory, I make grateful 

 acknowledgment of my indebtedness. 



A word as to localities. The marine Bryozoa were found especially 

 abundant at Newport on floating eel-grass in the cove and on the piles 

 of the wharf. The embryos of Cristatella and Plumatella were found in 

 colonies which literally covered the bottom of some parts of the south 

 or shady side of Trinity Lake, Pound Ridge, New York. They occur 

 especially in densely shaded and fairly deep water near the shore. 



The Gymnolsemata present many ditficulties to finer technique. They 

 possess a chitinous covering, often very thick, and frequently, in addition, 

 a calcarous skeleton. When the latter is present, picro-nitric acid mixed 

 with sea water is a fairly good fixing reagent ; when it is absent, hot cor- 

 rosive sublimate was most serviceable. The objects must be transferred 

 through the grades of alcoliol with extreme caution, to prevent the col- 

 lapse of the ectocyst. I used the chloroform-paraffin method of em- 

 bedding in order to make transfers more gradual at this stage. Some 

 difficulty was experienced in staining such small objects on the slide, since 

 the tissues are very loosely associated ; and on the other hand i7i toto 

 staining is unsatisfactory in some cases, owing to impenetrability of the 

 ectocyst. Often it was necessary to open the body cavity of each indi- 

 vidual by means of a sharp knife or needle. The best results were 

 obtained with alcoholic dyes like Kleinenberg's hsematoxylin and 

 Mayer's cochineal; although Ehrlich's hsematoxylin was often used 

 with success. 



II. Budding in Paludicella. 

 1. Architecture of the Stoci^- 



Paludicella, as is well known, occurs in quiet streams and forms 

 stocks on the under surfaces of stones and other objects. Seen with the 

 naked eye these stocks appear as a fine lacework, composed of constantly 

 branching lines of individuals. Some of the stocks which I have meas- 

 ured are over 25 mm. in length along their greatest diameter. 



