436 



SCIENCE 



[N. S. Vol. XLI. No. 105.5 



The answers given to these questions are: 



1. Previous to the stage of 4.5 mm. there are no 

 protoplasmic connections "between tube and myo- 

 tome in. Squalus embryos. 



2. Neurofibrillar substance is present in the first 

 protoplasmic connections between tube and myo- 

 tome. In the primary protoplasmic connections 

 appear deeply staining neurofibrils which may be 

 traced to bipolar neuroblasts within the neural 

 tube. The claim that the primary connections con- 

 sist of undifferentiated plasmodesmata therefore 

 is based upon inadequate neurological methods. 



3. In stages before protoplasmic connection be- 

 tween tube and myotome is effected certain medul- 

 lary cells in zones where later the nerve anlagen 

 make their appearance show in Bielchowsky-Paton 

 preparations a deeply-staining neuro-reticulum. 

 In slightly later stages when neuro-muscular con- 

 nection is established similar neuro-reticular cells 

 are found connected with neurofibrilla; extending 

 into the nerve anlagen in the manner characteris- 

 tic of medullary neuroblasts stained by specific 

 neuro-flbrillar stains. The evidence of the pres- 

 ence of similar neurofibrillar substance in all parts 

 of the nerve anlagen supports the inference that 

 the neuromuscular connections are established — 

 not by indifferent cells — but by medullary neuro- 

 blasts, as maintained by supporters of the Bidder- 

 Kupffer theory. Indifferent cells participate in 

 the formation of nerve anlagen only in more ad- 

 vanced stages by a process of migration from the 

 neural tube. 



The Components of the Fenestral Plate in. Nec- 



turus: H. D. Reed: 



In previous communications it has been pointed 

 out that in certain urodele families the sound- 

 transmitting apparatus consists of a single piece 

 resulting from gradual growth during larval and 

 early adult life. In such forms the plate is com- 

 pound. The stylus represents columella or the es- 

 traotie element, while the plate itself arises from 

 chondrification within the fenestral membrane and 

 therefore otic in nature. 



The fenestral plate in Neeturus has been con- 

 sidered as oolumella. It arises outside the ear 

 capsule and gradually comes to lie against the 

 fenestral membrane over the cephalic portion of 

 which it spreads through growth eventually filling 

 the fenestra at this level. Caudad the plate 

 tapers coming to a point at about the middle of 

 the fenestra. The plate thus formed is soon en- 

 cased in bone. About the margin of this triangu- 

 lar columellar plate cartilage is formed by 



ohondroblasts which arise in the fenestral mem- 

 brane. The matrix which is soon secreted is in- 

 vaded by bone deposited in continuity with the 

 previously formed bony case. Thus cell by cell the 

 definitive structure is completed by additions to 

 the margin of the columellar plate. The fenestral 

 plate is to be considered, therefore, as a compound 

 structure possessing both otic and extraotic ele- 

 ments and must be looked upon as a morphologic 

 intermediate of the condition found in Amhystoma 

 and the PlethodontidK. 

 Variations in the Says of Ten Thousand Star-Fish, 



Asterias ForiesU: Franklin D. Barkek. (With 



lantern.) 

 A New Dignetic Trematode from the Crayfish: 



John W. Scott. 



In 1827 Von Baer described a fiuke from the 

 crayfish to which he gave the name Distomum 

 cirrigerum. Warren ('03) described its anatomy 

 and development, and Sulowiow ('11) discussed 

 its structure and systematic position. During the 

 past two years trematodes from American cray- 

 fish have been secured; these are all encysted, sex- 

 ually mature, individuals. In certain points they 

 are quite similar to the European form, but the 

 differences are so striking as to place them in 

 different species. Wright ( '84) appears to have 

 been the first to observe the fiuke in this country, 

 but mistook it for D. nodulosum. Linton ( '92) 

 gives a brief description of immature specimens, 

 and calls attention to Wright 's mistake. The 

 American species differs from the European in 

 the following particulars. It has no conical or 

 plate-like eutieular scales; it has two lateral palp- 

 like extensions of the oral sucker, and four pa- 

 pillae; the esophagus is short, the gastric coeea 

 arising in front of the genital pit; the yolk glands 

 extend nearer the anterior end of the body; both 

 testes are median, or nearly so, and one lies in 

 front of the other; small eutieular denticles are 

 found on the oral sucker; the cerebral ganglia are 

 wider apart, the prostate gland better developed, 

 and the excretory bladder of somewhat different 



A full description of the new form, with a dis- 

 cussion of its probable systematic relationship, 

 will soon be published. 

 The Eeflex "Bleeding" of the Coccinellid Beetle, 



Epilachna Borealis: N. E. McIndoo. 

 The Gland of the Cla-sper in SharTcs: E. W. 



GUDGEE. 



In the claspers of sharks, on the inner and dor- 

 sal surface the tissues are modified to form a 



