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THE AMERICAN NATURALIST. [Vol. XXXVII 



The whole development of Lingula is preeminently direct, the mantle 

 lobes growing over the cephalic region ab initio. There is conse- 

 quently no inversion of the mantle lobes as in Cistella, Thecidium, etc. 

 The embryo is also two lobed instead of three, as in the latter 

 genera, the caudal lobe being absent in Lingula. "The shell is 

 formed at first as a circular lamella folded double along one of its 

 diameters, and is secondarily divided into two valves along the poste- 

 rior edge." This is in marked contrast with the method of shell origin 

 that obtains among the Articulata. In conclusion, attention is called 

 to the resemblance between the mode of cleavage in Lingula up to 

 the 32-celled stage and that of some species of Fhylactoloemata. 

 This is in harmony with the observations of Dr. Conklin above 

 referred to, as is also the fact that in Lingula there is no true seg- 

 mentation of the embryo. 



Mr. Yatsu's paper on the Histology of Lingula 1 gives a detailed 

 account of the several kinds of bodies found in the ccelomic fluid, 

 namely, the blood corpuscles, leucocytes, and spindle bodies. An 

 extended account is given of the latter — their form, occurrence, 

 development, and significance. They are shown to be metamor- 

 phosed blood corpuscles, " a cell whose nucleus has degenerated and 

 whose cytoplasm has turned into a fibrous structure" Their function 

 is excretory. 



A third paper by the same author 2 deals with the habits of 

 Lingula, and is extremely interesting. These forms live in mud flats 

 which are exposed at low water, and though ordinarily no trace of 

 them can be seen, their presence is sometimes detected by three 

 small holes in the mud. These holes must be evidently produced by 

 the setal tubes mentioned by Morse. The cirri of the brachia, 

 though not the brachia themselves, can be protruded from the front 

 of the shell. The life of Lingula may be as long as five years. 

 Yatsu mentions the extreme tenacity of life in this genus. In one 

 instance an influx of sediment that proved fatal to all the lamelli- 

 branchs of the locality had no effect upon the Lingulas. The plates 

 which accompany these three papers by Mr. Yatsu certainly testify 

 to his own and the lithographer's skill. They are models of clear- 



