AMONG SIMPLE SAUCODE ORGANISMS. 403 



The observations of Hertwig render it probable that the 

 simple extension of the colony witliout separation of the newly 

 formed zooids takes place by a longitudinal instead of a transverse 

 division of the body. Two or, in some cases, three segments 

 are thus formed. Of these, one remains in the old shell, the others 

 forsake it and excrete for themselves a new one, while all continue 

 in union by their common pseudopodial end, 



Cienkowski* has, in all important points, confirmed these obser- 

 vations. He finds further that the second cell-nucleus which 

 appears during the division of the shell-contents arises indepen- 

 dently, and not by the division of the mother nucleus. 



Among the genera of Thalamophora in which the shell possesses 

 a definite structure, Euglypha (fig. 7) may be regarded as the most 

 typical. This genus was founded by Dujardin, and Hertwig and 

 Lesser retain in its essential points the definition given by the 

 French observer. The Euglyphae are Ehizopoda with pointed fili- 

 form pseudopodia which show no granule-currents, and do not 

 anastomose with one another, but for the most part ramify dicho- 

 tomously. The oval or flask-shaped shell is a pure secretion from 

 the surface of the protoplasm, and remains unchanged under the 

 action of concentrated mineral acids and of alkalies. The termi- 

 nal orifice is, for the most part, finely dentate, and the solid and 

 inflexible walls of the shell have a sculpture which, as was first 

 pointed out by Carter and by "Wallich, is caused by spirally dis- 

 posed plates which, in all the forms examined by Hertwig and 

 Lesser, are hexagonal and in contact by their edges. 



In the protoplasm may be distinguished an anterior and a pos- 

 terior region. The former occupies nearly two thirds of the 

 whole. The protoplasm of the anterior region is finely granu- 

 lar ; it alone contains the foreign matter ingested for nutriment. 

 The protoplasm of the posterior third is homogeneous, but fre- 

 quently contains some darkly coloured granules of nearly uniform 

 size. In all cases ix, contains the cell-nucleus first observed by 

 Carter. This has the form so well known in the nucleus of the 

 Rhizopoda, that of a roundish or oval vesicle with a central homo- 

 geneous pale blue oval nucleolus. Included in the protoplasm, 

 at the boundary between the anterior and posterior regions, are 

 the contractile vacuoles, generally two or three in number. 



F. E. Schulze has studied these vacuoles in Euglypha alveolata, 



* " Ueber einige Rhizopoden und verwandte Organismen," Arch, fiir mikr. 

 Anat. 1876. 



34* 



