214 BULLETIN OF THE 



As the only figures which we have of Nanomia are of the young, my first 

 care was to obtain a figure (Plate I.) of the adult animal. 



The method by which a drawing of the outline of this large Nanomia was 

 made may have an interest to those engaged in the study of the Siphono- 

 phores. The outlines of Plate I. were drawn in the following way. 



The animal was placed in an upright glass jar, with flat sides, similar to 

 those of glass vessels used for the bath in photography. This glass receptacle 

 was placed in the bright sunlight, on a table between the observer and the 

 window, or some source of light. It was so placed that a well-defined shadow 

 of it was projected on the paper held a few inches back of the animal, on the 

 side of the glass opposite the window. The paper was tacked to a board held 

 upright and firm by simple means, which any one can devise. The shadow of 

 the Nanomia was so clearly defined that even the fainte.st lines of outline were 

 seen projected on the paper. There are times when a Siphonophore floating 

 in the water keeps almost perfectly quiet for some minutes. This is a good 

 opportunity to trace on the paper the lines of the shadow with a pencil. 

 Although I could not make the whole contour before a new movement of the 

 medusa, it was easy to draw the nectocalyces and sections of the polyp-stem 

 before the animal changed its attitude. 



The only trustworthy account which we have of Nanomia is the original 

 description by A. Agassiz.* This observer not only described the first long- 

 stemmed Physophore from American waters, but he also gave the first series 

 of recorded observations on the development of the young of any genus of 

 Siphonophores. 



From my own studies of Nanomia I am convinced that the adult of Nano- 

 mia has never been figured or described. The reasons for this belief will, I 

 hope, appear as I go on in my account. The description by A. Agassiz was 

 pioneer work in a field where later observations have been extensively made ; 

 yet for over fifteen years Nanomia was the only long-stemmed Physophore 

 known from the waters of the United States. His description has been 

 repeatedly copied, and his figure is widely used in general accounts of these 

 animals. It is found necessary to diff'er from one or two statements made in 

 the original description in i-egard to Nanomia. These diff'erences are specially 

 noted, and a redescription is not made of those points of anatomy where in the 

 main my account agrees with that already published. The fact that Nanomia 

 more than any other Siphonophore is used in text-books and general descrip- 

 tions of marine animals published in America to illustrate the general charac- 

 ter of the group, would seem an inducement to publish an}'' contributions 

 which might be made in regard to its embryology and anatomy. 



It may be well, at the very threshold of my description, to mention the 



* Tlie best account of the anatomy and embryolonry of Nanomia is in " North 

 American Acnleplire." Tliere are other notices of tlie same animal by tlie same 

 author, one of the best known of which is in " Seaside Studies," by Mrs. E. C. and 

 A. Agassiz. 



