1 88 Balanoglossiis. [zoe 



belongs to Mr. William Bateson/ a young English morphologist, 

 who studied the structure and development of an American species 

 found on our Atlantic coast; though it is an interesting fact that the 

 distinguished Russian already mentioned was the first to study in 

 detail the structure of the adult, he having published the results of 

 his investigations on this subject in the same year that his classical 

 Ascidian paper, mentioned above, appeared. 



We will give a short account of the structure, development, and 

 habits of the animal, and also consider briefly its claims to the right 

 of being raised from the ranks of the " lowly worm " to a place 

 among the nobler Chordata, which promotion was proposed by Mr. 

 Bateson, and has been adopted by several more recent writers. 



By the aid of Figs, i and 2 we may be able to get a fairly good idea 

 of the appearance and anatomy of the adult animal. The original 

 figure, here copied from Korschelt & Heider,-' was made by Alex- 

 ander Agassiz and represents the Atlantic coast species, B. Kowal- 

 evskii. The creature is divided into three very distinct regions: 

 the proboscis, pro.; the collar, col., and the abdomen, abd., which 

 is again composed of a pharyngeal or respiratory portion, and an 

 abdomen proper or digestive portion. The proboscis is a firm 

 muscular organ, cylindrical or somewhat conical in shape, 

 but varying considerably both in form and length in different 

 species; in most species it is, however, proportionally shorter 

 than in the one here represented. The proboscis is joined to 

 the collar by a short peduncle. In its normal condition the 

 collar is nearly cylindrical in shape, and, as with the proboscis,^ 

 there is nothing either in form, surface marking, or color, to readily 

 distinguish the dorsal from the ventral side. The mouth is ven- 

 trally situated, but its position at the anterior end of the collar at 

 the point of attachment of the peduncle to this latter is so effectually 

 shut in by a sort of rim-like projection on the anterior edge of the 

 collar that it is scarcely visible, particularly when the parts are in a 

 state of contraction. 



■^\Vm. Bateson. The Early Stages in the Development of Balanoglossus (sp. 

 incert). Quart. Journ. Micro. Sci., Vol. xxiv, Apr., 1884. Also: Continued 

 Account of the Later Stages in the Development of Balanoglossus Kowalevskii, 

 and of the Morphology of the Enteropneusta, ibid Vol. xxvi, p. 511, 1886. 

 Also: The Ancestry of the Chordata, ibid Vol. xxvi, p. 535, 1886. 



^ E. Korschelt und K. Heider, Lehrbuch der vergleichenden Entwicklungs- 

 geschichte der wirbellosen Thiere, erstes Heft, Jena, 1890. 



