No. I.] SENSE-ORGANS OF LUMBRICUS AGRICOLA. 22/ 



shown by the fact that the gland-cells were stained in his prep- 

 arations while they were always unstained in mine, and by the 

 fact that Lenhossek could not find a basement-membrane and 

 did not notice the basal cells of the epidermis, while both of 

 these structures showed in my preparations. Retzius ('92) 

 says, " freie Nervenendigungen sah ich ebenso wenig wie v. Len- 

 hossek im Hautepithel des Regenwurms." It is, however, 

 evident that he saw such a nerve-fibre in the buccal cavity, but 

 as he saw this appearance but once, judged himself mistaken. ^ 



1 After my work was completed and the account of it in the hands of the editor 

 of this Journal, a preliminary paper by Dr. Alexis Smirnow, entitled " Ueber freie 

 Nervenendigungen im Epithel des Regenwurms," appeared in Anat. Anzciger, Bd. 9, 

 No. 18 (June 23, 1894). In this paper Smirnow records his discovery of free- 

 ending nerve-fibres in the epidermis of Lumbricus. My own discovery of these 

 fibres was made in the spring of 1893, and briefly mentioned in a preliminary 

 account of my work which was read before the American Morphological Society 

 at the New Haven meeting in December, 1893. 



In the main Smirnow's work on these free nerve-endings confirms my own ; 

 but his account differs from mine in the following particulars : — 



1. Smirnow overlooks the presence of sense-organs and follows Lenhossek 

 and Retzius in ascribing the sensitiveness of Lumbricus to isolated nerve-cells. 

 These cells I regard as the constituent cells of epidermal sense-organs. I regard 

 Smirnow's statement (I.e., p. 574) concerning the striation and elevation of the 

 cuticular over the "sensibel Nervenzellen " as strong evidence of this. He says : 

 " Die Strichelung der Cuticula ist haufig scharfer ausgebildet an den Stellen, v.o 

 sich die ausseren Enden der Nervenzellen mit der Cuticula beriihren, worauf 

 bereits G. Retzius aufmerksam macht, ebenso wie auf die hiigelartige Verdickung 

 der Cuticula, die an diesen Stellen manchmal vorkommt. Ob diese Strichelung 

 von einer Canahsation der Cuticula abhangt, kann ich ebensowenig entscheiden 

 wie Prof. G. Retzius." My study has convinced me that these striations over the 

 "Nervenzellen" are truly due to canals in the cuticula, and that the hairs borne 

 by these cells pass through these canals to the exterior. The " hiigelartige Ver- 

 dickung " is, as I interpret it, the elevated summit of a sense-organ. 



2. I have never found the protoplasmic processes of the " Nervenzellen " very 

 long or forming a part of the " subepithelialen Plexus." In thick sections, bits of 

 the subepidermal network sometimes appear as if continuous with these pro- 

 cesses ; in every case in which I have been able to trace the protoplasmic processes 

 of the sense-cells, I have found that they end at or on the basement-membrare 

 under the sense-organ in which the cell they come from is situated, and that their 

 course is usually sinuous owing to the fact that they have to reach this membrar.e 

 by passing between the small basal cells of the sense-organ, — cells which Smirnow 

 does not mention. 



3. I do not find that the sensory fibres form a part of the subepidernial net- 

 work. I have always found that these fibres pass in bundles, without any con- 

 nection with other structures in the epidermis, directly to the nearest epidermal 

 nerve. 



