38 



PROF. AGASSIZ 7 S 



PLATE XXX 



isolated luue flower-like Pol v pus \tig. U), ot which 

 one is figured (fig. D) upon a larger scale, showing 

 that the tentacles, eight in number, are also fringed 

 like those Aleyonimn, being regularly arranged in 

 three pairs upon the two sides of the elongated 

 mouth, a seventh and eighth tentacle being in the 

 prolongation of the oral aperture. This animal is 

 of a beautiful purplish color, emitting in the dark 

 a most wonderful, soft, greenish-golden phosphor- 

 escent light. 



There is another type of Polypi very common 

 on the shores of Massachusetts and farther South, 

 the Actinia, of which one species (Actinia Margi- 

 aata, plate XX, DV is found upon logs along the 

 wharves in Boston harbor and upon the rocks at 

 Nahant, in great numbers. They are isolated ani- 

 mals, growing to a comparative!}' larger size than 

 the other Polypi; remarkable for their extraordi- 

 nary contractility, the body assuming constantly 

 new forms and new positions ; now entirely drawn 

 out in the shape of an elongated tube with a circle 

 of tentacles around the free extremity, (Fig. D) 

 then the tentacles rising and falling, or shutting 

 in and expanding ; next shortened and contracted 

 with the tentacles closed (Fig. E) ; or the external 

 envelope entirely shut over the inner part, pssum- 

 ing then a hemispheric shape, like round tubercles 

 sticking to the ground by their fleshy base. The 

 variations of color are as numerous as the changes 

 of form; upon the same spot may be seen brown 

 ones, and others dark brown or blackish, yellow- 

 is-hs purple, salmoa, rose-colored and more or less 



mottled, the tentacles presenting siternatiocs of 

 dark and lighter rings, or at least having their 

 tips differently colored than the lower part. 



That Yelella and Porpita, now generally ar- 

 ranged among Jelly fishes,will have to be removed 

 from the class of Aealephss and placed side by 

 side with the Actinia, will not escape the attention 

 of those who are familiar with these animals.* 



Recently, the Polypi have again been extensive-- 

 ly investigated by Prof Milne -Edwards, whose 

 name is always to be mentioned when speaking of 

 the lower animals, as scarcely any one has dene 

 more than he has in their investigation. Ehren- 

 burg has also largely contributed to our knowl- 

 edge of the Polypi, But no one has done more to 

 illustrate their natural history than Mr. James 

 Dana, of New Haven, Conn., who accompanied the 

 exploring expedition under Capt, Wilkes, and who* 

 has published the most elaborate work upon this 

 subject which has ever issued from the press. A 

 work, indeed, which will remain a standard of au- 

 thority in this department for many years to come. 



The embryonic growth of these animals has 

 been sin-died almost exclusively by Naturalist 

 living in countries which have been wanting ire 

 facilities for investigation, and are deprived of 

 privileges which Naturalists have enjoyed in other 

 parts of the world, where the animal kingdom is 

 more luxuriantly developed. 



It is on the shores of Norway and Sweden that 

 the most important investigations upon the em- 

 bryonic growth of these animals have been made,- 

 There, where the observer is neither attracted by 

 the variety of animals, nor by the possibility of 

 discovering easily new species, the interest of the 

 subject has drawn them into a deeper and more 

 thorough channel of investigation, which has en- 

 dowed science with a more extensive acquaintance 

 with all the difference of structure which is shown- 

 by the animals of those shores. And, indeedj far 

 from considering it an advantage to bs placed 

 upon a shore where new treasures are thrown: 

 abundantly into the hands of investigators, I think 

 it is, on the contrary, an unhappy inducement for 

 observers to devote their whole attention to the 

 multiplication of specific distinctions, without al^ 

 lowing time for the more important and more ex- 

 tensive investigation of the physiological phenom- 

 ena attending the life attending the development 

 of those beings. 



The structure of the Polypi can bs best exem- 

 plified in the Actinia (Plate XX, fig. !>) as they 

 are among the largest, and as they are now more- 

 extensively illustrated than any other type of the 

 class has been before. And what I have to say 

 of these animals will be scarcely more than a 

 repetition of what Dr. Jeffries Wynnan has pub- 

 lished in the work of Mr, Dana, already mention- 

 ed ; some few observations only, the result of my 

 own investigations, having been added to his,, 

 since the publication of that work. The body is 

 of father large sise for a Polype, measuring 



