June 8, 1883.] 



SCIENCE. 



511 



Thickness. 



Beneath the svirface-soil, yellowish clay, with 

 layers of gravel in the lower portion, and 

 in patches through it 20 ft. 



True drift clay, bluish, with smoothed and 

 striated gravel; small bowlders of lime- 

 Stone; one large bowlder of blue limestone 

 of several tons' weight; together with many 

 smaller ones which had been partially re- 

 moved 5 ft. 



Limestone in thin layers to level of railway, 3 to 7 ft. 



Above the bed of the river 61 ft. 



This localit}' is sixtj- miles south from the 

 crossing of the Ohio River bj- the grand mo- 

 raine. 



2. In Rock Castle Countj', at the summit of 

 the Knoxville branch of the Louisville and 

 Nashville R.R., between Roundstone Lick and 

 Pine Hill, is a hill of modified drift, mainlj- 

 composed of detritus derived from lower coal 

 conglomerate and limestone. The railway cut- 

 ting revealed some twelve feet in thickness of 

 this material. 



3. At the crossing of Rock Castle River 

 by the same railwaj', polished and striated 

 blocks of subcarbouiferous limestone in situ 

 were seen after removal of the superimposed 

 clays. The striation of these blocks may be 

 due to ice moving down the river, though it is 

 doubtful if river-ice has ever weight enough 

 to do much smoothing and striating work. 



4. At the Hazel Patch summit of the same 

 branch railroad, on the highest portion of the 

 Cumberland plateau in Laurel county, a cut of 

 the road revealed a low moraine composed of 

 fragments of carboniferous slates and sand- 

 stones, and of the upper coal of this portion 

 of the county. In riding over this plateau 

 twoj-ears ago, I encountered this moraine, and 

 then traced it east and west for some distance, 

 suspecting its ice-origin. Subsequent work on 

 the line of the railway confirmed my suspicions. 



5. In the summit between Laurel branch of 

 Rock Castle River, and Lj-nn Camp branch, a 

 heavj' bed of glacial elaj- was encountered, 

 showing the worn-off edges of coal-seams on 

 their northern aspect, and fragments mingled 

 with the claj's, similar to coal-beds and claj's 

 to be seen almost anj-where in Ohio. 



My notes of these two last localities having 

 been mislaid, I cannot describe the sections in 

 detail. 



These claj'-beds cannot be referred to clays 

 derived from decomposition of shales and 

 marls of the coal strata. The latter are al- 

 ways found in situ, while the glacial claj's may 

 repose upon coal, sand-rock, limestone, or anj' 

 other strata of the county, so that there is no 

 danger of confounding the two. If the recent 

 cuts of railways in construction and of those 



latel}' completed were closely examined, the 

 surface geologj' of Kentucky' would doubtless 

 reveal many other localities where glaciation 

 could be studied to advantage. 



R. P. Stevens. 



EARLY DEVELOPMENT OF REPTILES. 



W. F. K. Wbldon publishes a valuable article on 

 Lacerta muralis (Quart, journ. micr. .sc, xxiii. 134). 

 His clearness and conciseness contrast very agreea- 

 .bly with the prolixity of many embryologioal writ- 

 ings. At the close of segmentation the ectoderm 

 consists of cells very irregularly arranged, often two 

 layers deep. The entoderm is also irregular and 

 two or three cells thick. The area pellucida is formed 

 by the outer cells becoming more columnar, and the 

 inner cells more regular. Soon the posterior end of 

 the area is marked by the presence of the primi- 

 tive streak, which is a mass of closely packed cells, 

 exhibiting no division into layers. The blastopore 

 commences at the anterior end of this streak as a 

 pit, open above, closed below. The floor of the pit 

 breaks through, and the blastopore assumes its nor- 

 mal condition, forming a communication between the 

 exterior and the primitive entodermic cavity. The 

 mesoderiji arises as two lateral outgrowths from 

 the primitive streak, afterwards from the sides of 

 the blastopore, and the axial strip of invaginated hy- 

 poblast. Anteriorly the mesoblastic elements are 

 branched cells, which are budded off from the ento- 

 derm. (Do not these correspond to Hertwig's mes- 

 enchyma ?) Weldon confirms Balfour and Stahl's 

 account of the development of the allantois as a pro- 

 cess of the primitive streak. 



Having examined younger embryos than Braun, 

 Weldon is able to rectify the former's account of the 

 origin of the Wolffian duct and renal tubules. The 

 protovertebrae are connected by an intermediate cell- 

 mass with the lateral mesoblast. In this interme- 

 diate mass there appears a series of cavities, each 

 opposite a protovertebra, and separate from one 

 another. They are the segmental vesicles described 

 by Rathke and other writers. When twelve proto- 

 vertebrae are present, the Wolffian duct begins to 

 appear as a solid cord of cells, splitting off from the 

 intermediate cell-mass, and passing, therefore, into 

 the dorso-lateral wall of each segmental vesicle. The 

 duct develops, acquiring a lumen in the interverte- 

 bral spaces first; but, when there are fifteen proto- 

 vertebrae, it becomes a continuous canal through the 

 first eigiit segments, and acquires at the same time 

 communication witli each segmental vesicle. Back 

 of the eighth segment the development is similar, 

 except that the duct grows independently of the 

 vesicles. This agrees with Sedgwick's observations 

 on the process in birds and elasmobranchs. 



Another paper on this subject has been published 

 by Dr. H. Strahl [Arch. anat. plitjsioL, anat. ahtli., 

 1SS3, 1). As an introduction, he gives notices of 

 previous researches on the same theme. Then fol- 

 lows a chapter of general remarks, in which the ges- 

 tation, growth, and gross changes of the embryos, 

 and the manner of obtaining them, are considered. 

 The main part of the article is devoted to a detailed 

 account of the new observations, prefaced by a 

 summary of the results previously obtained by him- 

 self. The new part begins with the stage when 

 the blastopore or neurenteric canal is completely 

 formed. The principal new results may be sum 

 marized as follows: in the neurenteric canal, two 



