10 MARINE INVERTEBRATA OF GRAND MANAN. 



hundred or more were taken at a single haul of the dredge. It also occurs in 

 Welch Pool, and near Low Duck Island. I have nothing to add to the description 

 of Forbes and Goodsir, whose observations I have mostly repeated. 



ACAULIS, St. n. g. 



A. PRiMARius, St., n. s., Fig. 4. The remarkable polype for which this name is 

 proposed, which is probably the largest hydroid known, was observed at Grand 

 Manan in two successive stages of development. It was first taken early in August, 

 when it was of a sub-cylindrical form, tapering suddenly to a point at each ex- 

 tremity. At the upper extremity was the mouth, very small, a little below which 

 the tentacula commenced, scattered at first, but gradually increasing in number, 

 and somewhat in size. These tentacula were minute, very short, equalling in 

 length about one-sixth the thickness of the body, with large globular tips. They 

 occupied about two-thirds of the surface of the body; on the remainder below, 

 their places were supplied by the medusa buds, which were crowded, and much 

 larger than the tentacula, although as yet but little developed. The inferior ex- 

 tremity of the body terminated in a short, pointed, fleshy spike, free from append- 

 ages, from which exuded a tenacious mucus, by which it adhered to the subaque- 

 ous surfaces to which it might be applied. Around the base of this spike, and 

 immediately under the buds, were regularly arranged eight long gracefully-curved 

 cirriform processes, each equalling in length about half that of the body. These 

 appeared from their motions to be in this — the first or free stage of the animal's 

 existence — the locomotive organs. 



At a subsequent time, I met with several of these animals which presented a differ- 

 ent appearance. The tentacula were larger, especially in the region of the mouth, 

 at the now blunt extremity of the body ; and the medusa buds were in an advanced 

 state of development, soon to become free swimming individuals. The inferior 

 appendages had disappeared, and the body was firmly attached by a broad base, 

 and bore much resemblance to one of the ordinary Cort/nidoi deprived of its stalk. 

 In strong contractions, it assumed a shape approaching that of an hourglass. The 

 length of the animal, in this latter stage, was half an inch, the breadth two-tenths. 

 In the earlier stage, the dimensions were one-half these. 



It was dredged in the laminarian zone, from 5 to 15 f., attached to various 

 Rhodosperms, as Plilota, Chondrus, and Rhodymenia. Circumstances did not permit 

 me to ascertain the medusoid form of this polype, although I have my conjecture. 



I would here offer, for the judgment of zoologists, the following generalizations to 

 which I have been led by the consideration of two facts exhibited in the characters 

 of the animal above described. First, the basal cirri of the first stage are homo- 

 logous to the lower or exterior tentacula of Tubidaria, which I think is evident on 

 comparison of parts. Secondl}^, these cirri, or tentacula, are deciduous with the 

 growth of the animal, and do not appear in the second stage. Hence we should 

 consider the lubulariada', in which they are persistent, as lower in the scale. It 



